Method of controlling aspirator motive flow

ABSTRACT

Methods and systems are provided for controlling an aspirator shut-off valve in an engine of a hybrid vehicle. One example method includes opening the aspirator shut-off valve following a shut-down command to the engine when engine speed is between a first engine speed and a second engine speed, the first engine speed being lower than an idle speed and the second engine speed occurring before an imminent engine stop. The example method further includes not opening the aspirator shut-off valve between the first engine speed and the second engine speed if an oxygen content of an emission control device is at or near a threshold.

FIELD

The present invention relates to controlling motive flow through anejector coupled to an engine in a hybrid vehicle system.

BACKGROUND AND SUMMARY

Hybrid electric vehicles (HEV's) utilize a combination of an internalcombustion engine with an electric motor to provide the power needed topropel a vehicle. This arrangement provides improved fuel economy over avehicle that has only an internal combustion engine in part due to theengine being shut down during times when the engine operatesinefficiently, or is not otherwise needed to propel the vehicle. Duringthese conditions, the vehicle is transitioned from an engine mode to anelectric mode where the electric motor is used to provide all of thepower needed to propel the vehicle. When the driver power demandincreases such that the electric motor can no longer provide enoughpower to meet the demand, or if the battery state of charge (SOC) dropsbelow a certain level, the engine is restarted. Vehicle propulsion isthen transitioned from an electric mode to an engine mode.

Vehicle systems, including hybrid electric vehicles, may comprisevarious vacuum consumption devices that are actuated using vacuum. Thesemay include, for example, a brake booster, a fuel vapor canister etc.Vacuum used by these devices may be provided by a dedicated vacuum pump.In still other embodiments, one or more aspirators (alternativelyreferred to as ejectors, venturi pumps, jet pumps, and eductors) may becoupled in the engine system that may harness engine air flow and use itto generate vacuum.

Since aspirators are passive devices, they provide low-cost vacuumgeneration when utilized in engine systems. An amount of vacuumgenerated at an aspirator can be controlled by controlling the motiveair flow rate through the aspirator. While aspirators may generatevacuum at a lower cost and with improved efficiency as compared toelectrically-driven or engine-driven vacuum pumps, their use in engineintake systems has traditionally been constrained by both availableintake manifold vacuum and maximum throttle bypass flow. Some approachesfor addressing this issue involve arranging a valve in series with anaspirator, or incorporating a valve into the structure of an aspirator.Such valves may be referred to as aspirator shut-off valves (ASOVs) oraspirator control valves (ACVs). An opening amount of the valve isregulated to control the motive air flow rate through the aspirator, andthereby control an amount of vacuum generated at the aspirator. Bycontrolling the opening amount of the valve, the amount of air flowingthrough the aspirator and the suction air flow rate can be varied,thereby adjusting vacuum generation as engine operating conditions suchas intake manifold pressure change.

An example approach of controlling an aspirator control valve (ACV) in ahybrid electric vehicle is shown by Hirooka in U.S. Pat. No. 7,634,348.Herein, the ACV is opened when a controller in the hybrid electricvehicle determines that vehicle motion is primarily due to a motor ofthe hybrid electric vehicle. To elaborate, motive flow through theaspirator is allowed by opening the ACV when an engine-off condition isdetermined. Further, the ACV is opened after a pre-determined durationfollowing the engine shutdown command.

The inventors herein have identified potential issues with the aboveapproach to motive flow control in a hybrid electric vehicle. As anexample, the hybrid electric vehicle may experience engine shutdownshake due to excessive air flow as the engine comes to rest. Torsionalpulses may be caused by pistons compressing and expanding air that istrapped in engine cylinders and these pulses may be transmitted to thevehicle body. Accordingly, engine shutdown events can produce degradednoise, vibration and harshness (NVH), referred to as shutdown shake, aproblem that is exacerbated in hybrid vehicle systems as the engine isturned on and off repeatedly during operation of the vehicle. Motiveflow through the aspirator as the engine comes to a rest may contributeto NVH due to engine shutdown shake. In another example, oxygen storagein an emission control device may be increased due to air flow via theaspirator after engine shutdown. This increase in oxygen storage contentcan negatively affect emissions and catalyst performance.

The above issues may be addressed by a method of operating a hybridvehicle system, comprising, following a shut-down command to an engine,opening an aspirator control valve (ACV) between a first engine speedand a second engine speed, the first engine speed being lower than anidle speed and the second engine speed occurring immediately before animminent engine stop. In this way, NVH issues due to engine shutdownshake may be reduced.

Another example method for an engine in a hybrid vehicle comprises,following a first shutdown command to the engine, opening an aspiratorshut-off valve (ASOV) between a first engine speed and a second enginespeed, the second engine speed nominally higher than an engine stop, andfollowing a second shutdown command to the engine, closing ormaintaining closed the ASOV irrespective of engine speed.

As an example, an engine system in a hybrid electric vehicle (HEV) maybe configured with an aspirator for passive vacuum generation and anemission control device such as a three-way catalyst for reducingemissions. The engine system may be naturally aspirated wherein theaspirator is coupled across an intake throttle in an intake bypasspassage. In an alternate embodiment, the engine system may be a forcedinduction system including an intake compressor. Herein, the aspiratormay be coupled in a compressor bypass passage and may route a portion ofintake air from downstream of the intake compressor to upstream of theintake compressor. An aspirator shut-off valve (ASOV) may be coupledupstream (or downstream) of the aspirator to vary a motive flow throughthe aspirator. The ASOV may be opened for additional vacuum generationat the aspirator when a shutdown is commanded to the engine system.Specifically, an opening of the ASOV may be increased to enable motiveflow between a first engine speed and a second engine speed. Further,the first engine speed may be lower than an engine idle speed while thesecond engine speed is higher than an engine speed when an engine stopis imminent. A position of the ASOV following the shutdown command tothe engine may also be determined by an oxygen content of the three-waycatalyst. If the oxygen content in the three-way catalyst is at or abovean oxygen content threshold, the ASOV may be closed or maintained closedirrespective of engine speed being between the first engine speed andthe second engine speed.

In this way, additional vacuum may be generated and stored in a vacuumreservoir for future use by opening the ASOV as engine rotation slowsdown subsequent to an engine-off command in a HEV. However, by closingthe ASOV prior to an imminent engine stop, engine shutdown shake may bereduced. Further, by controlling air f low through the aspirator basedon the oxygen content stored in the emission control device, theperformance of the emission control device may be enhanced. As such, theASOV may be controlled in a simpler manner that is based on engine speedand oxygen content of the emission control device. Overall, theaspirator is able to meet the brake vacuum demand with improvedefficiency without degrading emissions compliance and the vehicleoperator's drive experience.

It will be understood that the summary above is provided to introduce insimplified form a selection of concepts that are further described inthe detailed description, which follows. It is not meant to identify keyor essential features of the claimed subject matter, the scope of whichis defined by the claims that follow the detailed description. Further,the claimed subject matter is not limited to implementations that solveany disadvantages noted above or in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A portrays a schematic depiction of a naturally aspirated enginesystem including an aspirator.

FIG. 1B illustrates a schematic depiction of a boosted engine systemincluding an aspirator.

FIG. 2 depicts an example hybrid vehicle system layout.

FIG. 3 presents a high level flow chart illustrating a routine forcontrolling the operation of an aspirator shut-off valve (ASOV) includedin the engine system of FIGS. 1A and 1B, according to the presentdisclosure.

FIG. 4 portrays an example flow chart illustrating a routine fordetermining if conditions are suitable for opening the ASOV.

FIG. 5 shows an example flow chart illustrating a routine fordetermining a position of the ASOV in a hybrid electric vehicle (HEV)system, in accordance with the present disclosure.

FIG. 6 depicts an example flow chart illustrating a routine forestablishing if engine speed is within a desired range for opening theASOV.

FIG. 7 presents an example flow chart illustrating a routine forverifying if a change in engine conditions has occurred to modify theposition of the ASOV.

FIG. 8 shows an example flow chart illustrating a routine for monitoringa temperature of the ASOV.

FIG. 9 depicts an example flow chart illustrating a routine fordetermining a desired current and voltage to be applied to the ASOV foractuation.

FIG. 10 (including FIGS. 10A and 10B) portrays an example flow chartillustrating a routine for determining a position of the ASOV based onan existing engine degradation condition.

FIG. 11 shows an example control operation of the ASOV based on enginespeed and the temperature of the ASOV, according to the presentdisclosure.

FIG. 12 presents an example control operation of the ASOV based on achange in intake manifold pressure.

FIG. 13 depicts an example control operation of the ASOV based on adetected engine degradation condition.

FIG. 14 illustrates an example control operation of the ASOV whenincluded in the HEV system of FIG. 2.

DETAILED DESCRIPTION

The following detailed description relates to methods and systems forgenerating vacuum at an aspirator coupled to an engine system, such asthe naturally aspirated engine system of FIG. 1A and the forcedinduction engine system of FIG. 1B. The engine system may be included ina hybrid electric vehicle (HEV), such as the hybrid vehicle system shownin FIG. 2. Vacuum generation at the aspirator may be regulated by anaspirator shut-off valve (ASOV) coupled either upstream or downstream ofthe aspirator. As such, an opening of the ASOV may be adjusted tocontrol motive flow through the aspirator, thus, controlling an amountof vacuum generated at the aspirator. A controller may be configured toperform one or more control routines, such as the example routines ofFIGS. 3-10, to open or close the ASOV based on engine conditions (FIGS.3 and 4) such as engine speed (FIG. 6), a temperature of the ASOV (FIG.8) which may depend on a current and voltage provided to the ASOV (FIG.9), and engine conditions in the HEV system (FIG. 5). A change in engineconditions may determine whether a position of the ASOV is to beadjusted (FIG. 7). Additionally, the controller may modify the positionof the ASOV based on determination of engine degradation conditions(FIG. 10). Example ASOV adjustments are described with reference toFIGS. 11-14.

Turning to FIG. 1A, it shows a schematic depiction of a spark ignitioninternal combustion engine 10. The embodiment of engine 10 shown in FIG.1A includes a naturally aspirated engine and does not include a boostingdevice. Engine 10 comprises a plurality of cylinders of which onecylinder 30 (also known as combustion chamber 30) is shown in FIG. 1A.

Cylinder 30 of engine 10 may include combustion chamber walls 32 withpiston 36 positioned therein. Piston 36 may be coupled to crankshaft 40so that reciprocating motion of the piston is translated into rotationalmotion of the crankshaft. Crankshaft 40 may be coupled to at least onedrive wheel of a vehicle via an intermediate transmission system (notshown). Further, a starter motor may be coupled to crankshaft 40 via aflywheel (not shown) to enable a starting operation of engine 10.

Combustion chamber 30 may receive intake air from intake manifold 46 viaintake passage 42 and may exhaust combustion gases via exhaust manifold48 and exhaust passage 19. Intake manifold 46 and exhaust manifold 48can selectively communicate with combustion chamber 30 via respectiveintake valve 52 and exhaust valve 54. In some embodiments, combustionchamber 30 may include two or more intake valves and/or two or moreexhaust valves.

In this example, intake valve 52 and exhaust valves 54 may be controlledby cam actuation via respective cam actuation systems 51 and 53. Camactuation systems 51 and 53 may each include one or more cams and mayutilize one or more of cam profile switching (CPS), variable cam timing(VCT), variable valve timing (VVT) and/or variable valve lift (VVL)systems that may be operated by controller 12 to vary valve operation.The angular position of intake and exhaust camshafts may be determinedby position sensors 55 and 57, respectively. Thus, the position of anintake cam may be determined by position sensor 55 while the position ofan exhaust cam may be determined by position sensor 57.

In alternative embodiments, intake valve 52 and/or exhaust valve 54 maybe controlled by electric valve actuation. For example, cylinder 30 mayalternatively include an intake valve controlled via electric valveactuation and an exhaust valve controlled via cam actuation includingCPS and/or VCT systems.

Fuel injector 66 is shown coupled directly to combustion chamber 30 forinjecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12 via electronic driver 68. In thismanner, fuel injector 66 provides what is known as direct injection offuel into combustion chamber 30. The fuel injector may be mounted in theside of the combustion chamber or in the top of the combustion chamber,for example. Fuel may be delivered to fuel injector 66 by a fuel system(not shown in FIG. 1A) including a fuel tank, a fuel pump, and a fuelrail. In some embodiments, combustion chamber 30 may alternatively oradditionally include a fuel injector arranged in intake manifold 46 in aconfiguration that provides what is known as port injection of fuel intothe intake port upstream of combustion chamber 30.

Ignition system 88 can provide an ignition spark to combustion chamber30 via spark plug 92 in response to spark advance signal SA fromcontroller 12, under select operating modes. Though spark ignitioncomponents are shown, in some embodiments, combustion chamber 30 or oneor more other combustion chambers of engine 10 may be operated in acompression ignition mode, with or without an ignition spark.

Intake manifold 46 is shown communicating with intake throttle 62 havinga throttle plate 64. In this particular example, the position ofthrottle plate 64 may be varied by controller 12 via a signal providedto an electric motor or actuator included with intake throttle 62, aconfiguration that is commonly referred to as electronic throttlecontrol (ETC). Intake throttle 62 may control air flow from intakepassage 42 to intake manifold 46 and combustion chamber 30 among otherengine cylinders. The position of throttle plate 64 may be provided tocontroller 12 by throttle position signal TP from throttle positionsensor 58. The intake passage 42 may include a mass air flow sensor 120and a barometric pressure sensor 121 for providing respective signalsMAF and BP to the controller 12. Barometric pressure sensor 121 may alsobe configured as a temperature/pressure sensor enabling it to measureintake air temperature (IAT) as well as barometric pressure (BP).

Further, in the depicted embodiment, an exhaust gas recirculation (EGR)system may route a desired portion of exhaust gas from exhaust passage19 to the intake manifold 46 via an EGR passage 82. The amount of EGRprovided may be varied by controller 12 via an EGR valve 80. Byintroducing exhaust gas to the engine 10, the amount of available oxygenfor combustion is decreased, thereby reducing combustion flametemperatures and reducing the formation of NOR, for example.

A positive crankcase ventilation (PCV) conduit 78 may couple a crankcase(not shown) to the intake manifold 46 such that gases in the crankcasemay be vented in a controlled manner from the crankcase. Further,evaporative emissions from a fuel vapor canister (not shown) may bepurged into intake manifold 46 through a fuel vapor purge conduit 76coupling the fuel vapor canister to the intake manifold.

Exhaust gas sensor 126 is shown coupled to exhaust passage 19 upstreamof emission control device 70. Sensor 126 may be any suitable sensor forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or COsensor. Emission control device 70 is shown arranged along exhaustpassage 19 downstream of exhaust gas sensor 126. Device 70 may be athree way catalyst (TWC), NOx trap, various other emission controldevices, or combinations thereof. Oxygen sensor 79 is shown coupled totail pipe 77 downstream of emission control device 70. An oxygen contentof the emission control device 70 may be estimated based on measurementsfrom exhaust gas sensor 126 and oxygen sensor 79.

Aspirator 20 may be coupled in conduit 23 (herein also referred to asbypass air intake passage 23 or a throttle bypass passage 23) acrossfrom intake throttle 62. Conduit 23 may be parallel to intake passage42, as shown in FIG. 1A, and may divert a portion of intake air receivedfrom downstream of air cleaner 133 to intake manifold 46 via aspirator20. The portion of air diverted from upstream of intake throttle 62 mayflow into first end 25 of conduit 23, through aspirator 20, and may exitinto intake manifold 46 downstream of intake throttle 62 at second end26 of conduit 23. Air flow through aspirator 20 creates a low pressureregion within the aspirator 20, thereby providing a vacuum source forvacuum reservoirs and vacuum consumption devices such as fuel vaporcanisters, brake boosters, etc. Aspirators (which may alternatively bereferred to as ejectors, venturis, jet pumps, and eductors) are,therefore, passive vacuum generating devices which can provide low-costvacuum generation when utilized in engine systems. The amount of vacuumgenerated may be dependent on a motive air flow rate through aspirator20. An aspirator shut-off valve (ASOV) 74 may be coupled to conduit 23downstream of aspirator 20, as shown in FIG. 1A. Alternatively, ASOV 74may be coupled upstream of aspirator 20. In yet other embodiments, ASOV74 may be integral to the aspirator 20 (e.g. the valve may be arrangedat a throat of the aspirator). ASOV 74 may also be termed an aspiratorcontrol valve or ACV 74.

ASOV 74 may be actively controlled to allow/disallow motive flow throughthe aspirator (in the case of a binary ASOV) or to reduce/increase flowthrough the aspirator (in the case of a continuously variable ASOV).Thus, by adjusting an opening of ASOV 74, a motive flow throughaspirator 20 can be varied, and an amount of vacuum drawn at aspiratorthroat can be modulated to meet engine vacuum requirements.

ASOV 74 may be an electrically actuated valve, and its state may becontrolled by controller 12 based on various engine operatingconditions. In one example, ASOV 74 may be a solenoid valve. Herein, theASOV may be actuated by a flow of current. As such, a default positionof the ASOV 74 may be a closed (or fully closed) position when nocurrent is supplied to the electrically actuated ASOV. Accordingly, achange in the default position of the ASOV (e.g. an opening of ASOV 74)may be achieved by supplying current to the ASOV. As will be describedin reference to FIG. 9, current and voltage values for actuating theASOV may be determined based on an underhood soak temperature.

In alternative embodiments, the ASOV may be a pneumatic (e.g.,vacuum-actuated) valve; herein, the actuating vacuum for the valve maybe sourced from the intake manifold and/or vacuum reservoir and/or otherlow pressure sinks of the engine system. In embodiments where the ASOVis a pneumatically-controlled valve, control of the ASOV may beperformed independent of a powertrain control module (e.g., the ASOV maybe passively controlled based on pressure/vacuum levels within theengine system).

Whether it is actuated electrically or with vacuum, ASOV 74 may beeither a binary valve (e.g. two-way valve) or a continuously variablevalve. Binary valves may be controlled either fully open or fully closed(shut), such that a fully open position of a binary valve is a positionin which the valve exerts no flow restriction, and a fully closedposition of a binary valve is a position in which the valve restrictsall flow such that no flow may pass through the valve. In contrast,continuously variable valves may be partially opened to varying degrees.Embodiments with a continuously variable ASOV may provide greaterflexibility in control of the motive flow through the aspirator, withthe drawback that continuously variable valves may be much more costlythan binary valves. In still other examples, ASOV 74 may be a gatevalve, pivoting plate valve, poppet valve, or another suitable type ofvalve.

The state of ASOV 74 (e.g., open or closed) may be determined based onvarious engine operating conditions as will be described in more detailin the disclosure with reference to FIGS. 3-14. Controller 12 may beoperatively coupled to ASOV 74 to actuate ASOV 74 between an open orclosed position (or to assume any position there-between for acontinuously variable valve). In a first example, the controller mayactuate the ASOV based on a vacuum level in a vacuum reservoir, such asa brake booster. For example, vacuum generation via the aspirator may beactivated by actuating open the ASOV when vacuum levels in the brakebooster are below a threshold. In a second example, the ASOV may becontrolled based on a desired air flow in the engine intake. Toelaborate, the ASOV may be closed when an air flow rate into the intakemanifold is greater than desired which may result in extra fuel beinginjected. While the above examples of controlling the ASOV may besuitable for routine engine operation, these control methods may notallow sufficient testing of the aspirator or the ASOV during emissionstesting procedures. As such, the ASOV may not be actuated duringemissions testing and/or diagnostic procedures when ASOV control isbased upon a vacuum level in the brake booster or upon a desired airflow in the intake.

Accordingly, the present disclosure describes ASOV control methods thatare at least partially based on engine speed. For example, thecontroller may command the ASOV 74 to an open position (from a moreclosed position) when engine speed is between a first, lower speed and asecond, higher speed. By opening the ASOV based on engine speed,conditions where the ejector motive flow can cause air flow greater thandesired are reduced (e.g., minimized). Since an air flow rate that isgreater than desired leads to extra fuel being injected, controlling airflow via the ASOV may improve engine performance and fuel economy.Further still, ASOV actuation during emissions testing procedures isassured when ASOV control is based on engine speed. Thus, diagnostics ofthe ASOV (and the aspirator) may be ensured while simultaneouslyassessing the impact of the ASOV (and aspirator) on emissions of thevehicle.

For an electrically actuated ASOV, the controller may also regulate theactuation of the ASOV based on a temperature of the ASOV. For example,the ASOV may be closed (from open) when the temperature of the ASOV ishigher than a threshold. In yet another example, a different controlalgorithm for modulating the ASOV may be utilized based on detection ofengine degradation conditions. An alternative control method may beemployed for a hybrid electric vehicle.

Returning to FIG. 1A, vacuum generated by aspirator 20 may be directedto vacuum reservoir 138 and brake vacuum reservoir 184 (also termed,brake accumulator 184) in brake booster 140. Vacuum reservoir 138 mayreceive vacuum via passage 73 through first check valve 63 located infirst conduit 93. The first check valve 63 allows air flow from vacuumreservoir 138 towards aspirator 20 and blocks air flow from aspirator 20towards vacuum reservoir 138. Sensor 125 may estimate a level ofpressure (or a level of vacuum) within vacuum reservoir 138. As such,sensor 125 may be a pressure sensor or a vacuum sensor. While thedepicted embodiment shows first check valve 63 as a distinct valve, inalternate embodiments of the aspirator, check valve 63 may be integratedinto the aspirator. Brake accumulator 184 may receive vacuum fromaspirator 20 via passage 73 through second check valve 94 coupled insecond conduit 65. An available pressure in the brake accumulator 184may be estimated by a vacuum sensor 127 (or pressure sensor 127).Controller 12 may thus receive pressure level readings from each ofsensor 125 and 127. In alternative embodiments, brake accumulator 184may receive vacuum directly from vacuum reservoir 138.

Brake accumulator 184 may be an internal vacuum reservoir in brakebooster 140 which in turn may be coupled to vehicle wheel brakes (notshown). The vacuum in brake accumulator 184 may amplify force providedby vehicle operator 196 via brake pedal 150 to master cylinder forapplying vehicle brakes (not shown). A position of the brake pedal 150may be monitored by a brake pedal sensor 154. Vacuum reservoir 138 maybe coupled to one or more engine vacuum consumption devices. Forexample, the vacuum reservoir 138 may be coupled to one or more of acanister purge valve (not shown), a charge motion control valve (notshown), and a turbine wastegate actuator in a boosted engine (not shownin FIG. 1A).

Though not shown in FIG. 1A, in other examples, vacuum reservoir 138 andbrake accumulator 184 may be directly coupled to intake manifold 46 viaseparate passages. That is, brake accumulator 184 may be directlycoupled to intake manifold via a first passage distinct from a secondpassage directly coupling vacuum reservoir 138 to intake manifold 46.Further, the first and the second passages may not include aspirator 20and may bypass aspirator 20. The vacuum reservoir 138 and brakeaccumulator 184 may receive vacuum from the intake manifold 46 whenintake manifold vacuum is deeper than the vacuum generated at theaspirator or when the aspirator is not generating vacuum.

Controller 12 is shown in FIG. 1A as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106, random access memory 108, keep alive memory 110, and aconventional data bus. Controller 12 commands various actuators such asthrottle plate 64, ASOV 74, EGR valve 80, fuel injector 66 and the like.Controller 12 is shown receiving various signals from sensors coupled toengine 10, in addition to those signals previously discussed, including:engine coolant temperature (ECT) from temperature sensor 112 coupled tocooling sleeve 114; position sensor 194 coupled to an accelerator pedal192 for sensing accelerator position adjusted by vehicle operator 196; ameasurement of engine manifold pressure (MAP) from pressure sensor 122coupled to intake manifold 46; a measurement of intake air temperatureand barometric pressure (BP) from temperature/pressure sensor 121coupled to intake passage 42; a measurement of vacuum in brake vacuumreservoir 184 from pressure sensor 127, a measurement of vacuum invacuum reservoir 138 from pressure sensor 125, a profile ignition pickupsignal (PIP) from Hall effect sensor 118 (or other type) coupled tocrankshaft 40; a measurement of air mass entering the engine from massair flow sensor 120; and a measurement of throttle position from sensor58.

Controller 12 may also receive communication from exhaust gas sensor 126and oxygen sensor 79 which may be used to estimate an oxygen storagecapacity of emission control device 70. Engine position sensor 118 mayproduce a predetermined number of equally spaced pulses every revolutionof the crankshaft from which engine speed (RPM) can be determined.Storage medium read-only memory 106 in controller 12 can be programmedwith computer readable data representing instructions executable byprocessor 102 for performing the methods described below, as well asother variants that are anticipated but not specifically listed. Examplemethods and routines are described herein with reference to FIGS. 3-10.

FIG. 1B depicts an example engine system 11 including a boosted engine.Engine system 11 is similar to engine system 10 of FIG. 1A differingprimarily in the positioning of the aspirator, and inclusion of aturbocharger and a high pressure exhaust gas recirculation (HP-EGR)conduit. Therefore, engine components previously introduced in FIG. 1Aare numbered similarly in FIG. 1B and not reintroduced.

Engine 11 includes a compression device such as a turbocharger orsupercharger including at least a compressor 162 arranged along intakepassage 42. For a turbocharger, compressor 162 may be at least partiallydriven by an exhaust turbine 164 (e.g. via a shaft) arranged alongexhaust passage 19. Compressor 162 draws air from intake passage 42 tosupply boost chamber 144. Exhaust gases spin exhaust turbine 164 whichis coupled to compressor 162 via shaft 161. For a supercharger,compressor 162 may be at least partially driven by the engine and/or anelectric machine, and may not include an exhaust turbine. Thus, theamount of compression provided to one or more cylinders of the enginevia a turbocharger or supercharger may be varied by controller 12.

A wastegate 168 may be coupled across exhaust turbine 164 in aturbocharger. Specifically, wastegate 168 may be included in a bypasspassage 166 coupled between an inlet and outlet of the exhaust turbine164. By adjusting a position of wastegate 168, an amount of boostprovided by the exhaust turbine may be controlled.

Further, in the example engine system of FIG. 1B, aspirator 21 may becoupled in conduit 28 (herein also referred to as compressor bypasspassage 28) across from compressor 162. Conduit 28 may be parallel tointake passage 42, as shown in FIG. 1B, and may divert a portion ofboosted air from downstream of compressor 162 and upstream of intakethrottle 62 to upstream of compressor 162 via aspirator 21. The portionof compressed air diverted from downstream of compressor 162 (andupstream of intake throttle 62) may flow into first end 29 of conduit28, through aspirator 21, and may exit into intake passage 42 upstreamof compressor 162 at second end 27 of conduit 28. Air flow throughaspirator 21 creates a low pressure region within the aspirator 21,thereby providing a vacuum source for vacuum reservoirs and vacuumconsumption devices such as fuel vapor canisters, brake boosters, etc.The amount of vacuum generated by aspirator may be dependent on a motiveair flow rate through aspirator 21. An aspirator shut-off valve (ASOV)74 may be coupled to compressor bypass passage 28 upstream of aspirator21, as shown in FIG. 1B. Alternatively, ASOV 74 may be coupleddownstream of aspirator 21. Further, ASOV 74 may be modulated bycontroller 12, as mentioned earlier in reference to FIG. 1A, to vary alevel of vacuum generated at aspirator 21. As such, control of ASOV 74may be based on engine speed, the temperature of the ASOV, and otherconditions that will be described below in reference to FIGS. 3-14.Similar to FIG. 1A, vacuum generated at aspirator 21 may be supplied toeach of vacuum reservoir 138 and brake accumulator 184.

It will be appreciated herein that though FIG. 1B shows aspirator 21coupled across from compressor 162 in conduit 28 (or compressor bypasspassage 28), other boosted engine embodiments may include aspirator 21coupled across intake throttle 62 as shown in the example embodiment ofthe naturally aspirated engine of FIG. 1A. Alternative embodiments mayinclude multiple ejectors coupled in different positions within theengine system. These multiple ejectors may be combined via check valvesto provide desired levels of vacuum.

Engine 11 may include a high pressure EGR (HP-EGR) system forrecirculating a portion of exhaust gas from the exhaust manifold to theintake manifold, specifically, from the engine exhaust, upstream ofexhaust turbine 164, to intake manifold 46, downstream of each of intakethrottle 62 and compressor 162. The HP-EGR system may include a HP-EGRconduit 84 and a HP-EGR valve 158 configured to control an amount ofexhaust gas recirculated along HP-EGR conduit 84. Though not shown inFIG. 1B, engine 11 may also include a low pressure EGR (LP-EGR) systemfor recirculating a portion of exhaust gas from the exhaust manifold tothe intake manifold, specifically, from the engine exhaust, downstreamof exhaust turbine 164, to the engine intake, upstream of intakecompressor 162.

Controller 12 of FIG. 1B may be similar to controller 12 shown in FIG.1A. However, controller 12 of FIG. 1B may command HP-EGR valve 158 andwastegate 168 in addition to commands to various actuators such asthrottle plate 64, ASOV 74, fuel injector 66 and the like. Further,controller 12 of FIG. 1B may receive signals from sensors previouslyintroduced in FIG. 1A as well as a measurement of throttle inletpressure (or boost pressure) from sensor 123 coupled to boost chamber144 downstream of compressor 162 in engine 11.

It will be appreciated that though the present disclosure may refer toengine 10 in the following description, the remaining description mayalso apply to engine 11 of FIG. 1B unless specifically noted.

In some embodiments, the engine (e.g. engine 10 or engine 11) may becoupled to an electric motor/battery system in a hybrid vehicle. Thehybrid vehicle may have a parallel configuration, series configuration,or variation or combinations thereof. Further, in some embodiments,other engine configurations may be employed, for example a dieselengine.

FIG. 2 illustrates an example vehicle propulsion system 200. Vehiclepropulsion system 200 includes a fuel burning engine 10 and a motor 220.As a non-limiting example, engine 10 may comprise an internal combustionengine and motor 220 may comprise an electric motor. Engine 10 ofvehicle propulsion system 200 may be engine 10 depicted in theembodiment of FIG. 1A or engine 10 in the embodiment of FIG. 1B. Motor220 may be configured to utilize or consume a different energy sourcethan engine 10. For example, engine 10 may consume a liquid fuel (e.g.gasoline) to produce an engine output while motor 220 may consumeelectrical energy to produce a motor output. As such, a vehicle withvehicle propulsion system 200 may be referred to as a hybrid electricvehicle (HEV).

Vehicle propulsion system 200 may utilize a variety of differentoperational modes depending on operating conditions encountered by thevehicle propulsion system. Some of these modes may enable engine 10 tobe maintained in an “OFF” state (i.e. set to a deactivated state withengine at rest) where combustion of fuel at the engine is discontinued.For example, under select operating conditions, motor 220 may propel thevehicle via drive wheel 230 as indicated by arrow 222 while engine 10 isdeactivated.

During other operating conditions, engine 10 may be set to a deactivatedstate (as described above) while motor 220 may be operated to chargeenergy storage device 250. For example, motor 220 may receive wheeltorque from drive wheel 230 as indicated by arrow 222 where the motormay convert the kinetic energy of the vehicle to electrical energy forstorage at energy storage device 250 as indicated by arrow 224. Thisoperation may be referred to as regenerative braking of the vehicle.Thus, motor 220 can provide a generator function in some embodiments.However, in other embodiments, generator 260 may instead receive wheeltorque from drive wheel 230, where the generator may convert the kineticenergy of the vehicle to electrical energy for storage at energy storagedevice 250 as indicated by arrow 262. During still other operatingconditions, engine 10 may be operated by combusting fuel received fromfuel system 240 as indicated by arrow 242. For example, engine 10 may beoperated to propel the vehicle via drive wheel 230 as indicated by arrow212 while motor 220 is deactivated. During other operating conditions,both engine 10 and motor 220 may each be operated to propel the vehiclevia drive wheel 230 as indicated by arrows 212 and 222, respectively. Aconfiguration where both the engine and the motor may selectively propelthe vehicle may be referred to as a parallel type vehicle propulsionsystem. Note that in some embodiments, motor 220 may propel the vehiclevia a first set of drive wheels and engine 10 may propel the vehicle viaa second set of drive wheels.

In other embodiments, vehicle propulsion system 200 may be configured asa series type vehicle propulsion system, whereby the engine does notdirectly propel the drive wheels. Rather, engine 10 may be operated topower motor 220, which may in turn propel the vehicle via drive wheel230 as indicated by arrow 222. For example, during select operatingconditions, engine 10 may drive generator 260, which may in turn supplyelectrical energy to one or more of motor 220 as indicated by arrow 214or energy storage device 250 as indicated by arrow 262. As anotherexample, engine 10 may be operated to drive motor 220 which may in turnprovide a generator function to convert the engine output to electricalenergy, where the electrical energy may be stored at energy storagedevice 250 for later use by the motor.

Fuel system 240 may include one or more fuel tanks 244 for storing fuelon-board the vehicle. For example, fuel tank 244 may store one or moreliquid fuels, including but not limited to: gasoline, diesel, andalcohol fuels. In some examples, the fuel may be stored on-board thevehicle as a blend of two or more different fuels. For example, fueltank 244 may be configured to store a blend of gasoline and ethanol(e.g. E10, E85, etc.) or a blend of gasoline and methanol (e.g. M10,M85, etc.), whereby these fuels or fuel blends may be delivered toengine 10 as indicated by arrow 242. Thus, liquid fuel may be suppliedfrom fuel tank 244 to engine 10 of the motor vehicle shown in FIG. 2.Still other suitable fuels or fuel blends may be supplied to engine 10,where they may be combusted at the engine to produce an engine output.The engine output may be utilized to propel the vehicle as indicated byarrow 212 or to recharge energy storage device 250 via motor 220 orgenerator 260.

In some embodiments, energy storage device 250 may be configured tostore electrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including cabinheating and air conditioning, engine starting, headlights, cabin audioand video systems, etc. As a non-limiting example, energy storage device250 may include one or more batteries and/or capacitors.

Control system 12 (also termed herein, controller 12) may communicatewith one or more of engine 10, motor 220, fuel system 240, energystorage device 250, and generator 260. As will be described by theprocess flow of FIG. 5, control system 12 may receive sensory feedbackinformation from one or more of engine 10, motor 220, fuel system 240,energy storage device 250, and generator 260. Further, control system 12may send control signals to one or more of engine 10, motor 220, fuelsystem 240, energy storage device 250, and generator 260 responsive tothis sensory feedback. Control system 12 may receive an indication of anoperator requested output of the vehicle propulsion system from avehicle operator 196. For example, control system 12 may receive sensoryfeedback from pedal position sensor 194 which communicates with pedal192. Pedal 192 may refer schematically to a brake pedal and/or anaccelerator pedal.

Energy storage device 250 may periodically receive electrical energyfrom a power source 280 residing external to the vehicle (e.g. not partof the vehicle) as indicated by arrow 284. As a non-limiting example,vehicle propulsion system 200 may be configured as a plug-in hybridelectric vehicle (HEV), whereby electrical energy may be supplied toenergy storage device 250 from power source 280 via an electrical energytransmission cable 282. During a recharging operation of energy storagedevice 250 from power source 280, electrical transmission cable 282 mayelectrically couple energy storage device 250 and power source 280.While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 282 may disconnected between power source280 and energy storage device 250. Control system 12 may identify and/orcontrol the amount of electrical energy stored at the energy storagedevice, which may be referred to as the state of charge (SOC). Energystorage device 250 may also be termed a battery.

In other embodiments, electrical transmission cable 282 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 250 from power source 280. For example, energy storage device 250may receive electrical energy from power source 280 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 250 from a power source that doesnot comprise part of the vehicle. In this way, motor 220 may propel thevehicle by utilizing an energy source other than the fuel utilized byengine 10.

Fuel system 240 may periodically receive fuel from a fuel sourceresiding external to the vehicle. As a non-limiting example, vehiclepropulsion system 200 may be refueled by receiving fuel via a fueldispensing device 270 as indicated by arrow 272. In some embodiments,fuel tank 244 may be configured to store the fuel received from fueldispensing device 270 until it is supplied to engine 10 for combustion.In some embodiments, control system 12 may receive an indication of thelevel of fuel stored at fuel tank 244 via a fuel level sensor. The levelof fuel stored at fuel tank 244 (e.g. as identified by the fuel levelsensor) may be communicated to the vehicle operator, for example, via afuel gauge or indication in a vehicle instrument panel 296.

The vehicle propulsion system 200 may also include an ambienttemperature/humidity sensor 298, and a roll stability control sensor,such as a lateral and/or longitudinal and/or yaw rate sensor(s) 299. Thevehicle instrument panel 296 may include indicator light(s) and/or atext-based display in which messages are displayed to an operator. Thevehicle instrument panel 296 may also include various input portions forreceiving an operator input, such as buttons, touch screens, voiceinput/recognition, etc. For example, the vehicle instrument panel 296may include a refueling button 297 which may be manually actuated orpressed by a vehicle operator to initiate refueling. For example, asdescribed in more detail below, in response to the vehicle operatoractuating refueling button 297, a fuel tank in the vehicle may bedepressurized so that refueling may be performed.

In an alternative embodiment, the vehicle instrument panel 296 maycommunicate audio messages to the operator without display. Further, thesensor(s) 299 may include a vertical accelerometer to indicate roadroughness. These devices may be connected to control system 12. In oneexample, the control system may adjust engine output and/or the wheelbrakes to increase vehicle stability in response to sensor(s) 299.

Now turning to FIG. 3, an example routine 300 is shown for operating anaspirator control valve (ACV) coupled to an intake bypass passage eitherupstream of or downstream of (or integral to) an aspirator, such as inFIG. 1A. Routine 300 may also be utilized for controlling an ACV coupledto a compressor bypass passage in a boosted engine, such as engine 11 ofFIG. 1B. The routine enables motive flow through the aspirator to beadjusted by modulating an opening of the ACV based on engine conditions.

At 304, the routine includes estimating and/or measuring engine and/orvehicle operating conditions. These include, for example, engine speed,engine temperature, atmospheric conditions (temperature, BP, humidity,etc.), MAP, boost pressure (in a boosted engine), desired torque, EGR,battery state of charge (SOC), etc.

At 306, routine 300 may determine if engine conditions permit openingthe ACV (from a closed position). Specifically, an opening of the ACVmay be increased to enable vacuum generation if suitable engineconditions are present. In the example of the ACV being a binary valve(e.g. two-way valve), the routine may determine if the ACV may beadjusted to a fully open position from a fully closed position. If theACV is a continuously variable valve, the routine may determine if theACV can be modulated from the fully closed position to a positionbetween fully closed and fully open. In one example, a suitable enginecondition for opening the ACV may be an engine speed higher than atransmission lugging limit. In another example, a suitable enginecondition may include MAP lower than throttle inlet pressure (TIP). Asdescribed earlier, ACV control may not depend on a level of storedvacuum in a vacuum reservoir. The controller may activate routine 400 ofFIG. 4 to determine if conditions are suitable for opening the ACV at306. If it is determined that suitable conditions do not exist foropening the ACV, routine 300 progresses to 308 to wait for appropriateengine conditions and the ACV may not be opened. In one example, aprevious position of the ACV may be maintained or the ACV may beadjusted to a more closed position based on existing engine conditions.

However, if it is determined that the ACV can be opened, routine 300continues to 310 where the ACV is opened for vacuum generation. Forexample, the opening of the ACV may be increased to enable a highermotive flow through the aspirator. As such, the ACV may be asolenoid-controlled valve. Actuating the ACV to an open position maycomprise flowing a current to energize the solenoid. Further, thecontroller may actuate the ASOV solenoid in an opening direction.Opening the valve may include fully opening the valve or moving thevalve to a more open position from a closed position (e.g. from fullyclosed). It will be noted that in the described example, a defaultposition of the ACV may be a closed position when there is no flow ofcurrent to the solenoid. In other examples, the ACV may be acontinuously variable valve where a degree of opening of the ACV may beadjusted between a fully open, a fully closed position, and any positiontherebetween). As a result of the increased motive flow through theaspirator due to the opening of the ACV, a larger amount of vacuum maybe drawn at the aspirator.

At 312, routine 300 may determine if a change in engine conditions hasoccurred that may entail closing the ACV. For example, the engine speedmay be lower than the transmission lugging limit. In another example,the MAP may be higher than the TIP in the example of a boosted engine.The controller may activate routine 700 of FIG. 7 at 312 to determine ifengine conditions have changed sufficiently to close the ACV.

If it is determined that engine conditions have not changed, routine 300proceeds to 314 to maintain the ACV in its open position (with theincreased opening of the ACV at 310) for continued vacuum generation.Routine 300 may then return to 312 to monitor any change in engineconditions which may involve closing the ACV.

Alternatively, if it is determined at 312 that a change in engineconditions has resulted in a demand for closing the ACV, routine 300continues to 316 to close the ACV e.g. by discontinuing the flow ofcurrent. For example, the ACV may be adjusted to the fully closedposition from the fully open position. In another example, the ACV maybe moved to a mostly closed position from a mostly open position. In theexample of the solenoid ACV, current flow to the solenoids may be ceasedcausing a closure of the ACV impeding motive flow through the aspirator.Routine 300 then ends.

Turning now to FIG. 4, it presents routine 400 for determining ifsuitable engine conditions are prevalent for opening the ACV. Asmentioned earlier, the controller may activate routine 400 at 306 ofroutine 300 in FIG. 3. Specifically, routine 400 assesses engine speed,manifold pressure (in a boosted engine), degradation conditions, etc. todetermine a position of the ACV.

At 404, it may be determined if the vehicle system is a hybrid vehicle.If yes, routine 400 proceeds to 406 where the ACV position is determinedbased on routine 500 of FIG. 5. Specifically, the ACV position may bemodulated in a distinct manner in a hybrid vehicle system based onengine-on conditions and engine shutdown conditions. For example, anengine shutdown opportunity may be used to generate additional vacuumbefore the engine comes to rest. Routine 400 may then continue to 410.

If it is determined at 404 that the vehicle system is not a hybridvehicle, routine 400 proceeds to 408 to determine if the engine speed iswithin a desired range. Routine 600 of FIG. 6 may be activated fordetermining if the speed of rotation of the engine is between a first,lower speed and a second, higher speed.

Referring now to FIG. 6, routine 600 is depicted herein for measuringengine speed and determining if engine speed is within a suitable rangeallowing the ACV to be opened. At 602, routine 600 may estimate ormeasure engine speed. As such, engine speed may be measured based on aprofile ignition pickup signal (PIP) from a Hall effect sensor (e.g.Hall effect sensor 118 of engine 10 and engine 11) coupled to acrankshaft. Hall effect sensor 118 may produce a predetermined number ofequally spaced pulses every revolution of the crankshaft from whichengine speed (RPM) can be determined.

Next at 604, routine 600 may determine if the measured or estimatedengine speed falls in a desired range between a first, lower speed, Sp_1and a second, higher speed, Sp_2. For example, the first, lower speed,Sp_1 may be based on a transmission lugging limit. The transmissionlugging limit may be a speed below which the engine may experiencelugging. As such, the transmission lugging limit may be a minimum speedthat reduces vibrations in a driveline. Noise and vibrations may beproduced in the transmission when the engine speed is significantlylower for a given engine load. In one example, the transmission lugginglimit (and Sp_1) may be 1250 RPM. In another example, the transmissionlugging limit (and Sp_1) may be 1500 RPM. The second, higher speed, Sp_2may be based on a redline speed. Redline speed refers to apre-determined maximum limit on engine speed for a given engine whereinoperating the given engine at a speed higher than redline may causesignificant engine component degradation. In one example, redline speed(and Sp_2) may be 6000 RPM. In another example, redline speed (and Sp_2)may be 7000 RPM.

If it is confirmed at 604 that the estimated or measured engine speed isbetween Sp_1 and Sp_2, routine 600 continues to 608 to determine thatengine speed is within the desired range. Herein, the ACV may be opened(or the opening of the ACV may be increased) if other engine conditionsthat conflict with opening the ACV are absent. However, if it isdetermined that engine speed is either lower than Sp_1 or higher thanSp_2, routine 600 proceeds to 606 to determine that engine speed is notwithin the desired range. As such, the ACV may not be opened (and may beclosed, if open) if engine speed is either lower than Sp_1 or higherthan Sp_2. Routine 600 may then end. Thus, routine 600 may determine ifengine speed is within the desired range and the result may be used byroutine 400 of FIG. 4.

Returning to 408 in routine 400, if it is determined that the engine isnot within the desired range, routine 400 continues to 414 where the ACVmay not be opened and may be retained at a closed position (or may beclosed, if open). Thus, the ACV may not be adjusted to an open positionand may be fully closed. In other words, the opening of the ACV may notbe increased. Routine 400 may then proceed to 416.

However, if it is determined at 408 that engine speed is within thedesired range, routine 400 continues to optional step 410 in a boostedengine where it may confirm that boosted conditions exist in the enginealong with manifold absolute pressure (MAP) being lower than or equal tothe TIP. Manifold pressure may be estimated by manifold pressure sensor(such as pressure sensor 122 of FIGS. 1A and 1B) while throttle inletpressure (or boost chamber pressure) may be determined by a throttleinlet pressure sensor such as TIP sensor 123 of FIG. 1B. If MAP isdetermined to be higher than TIP (e.g. when engine exits boostedconditions when TIP=barometric pressure), routine 400 progresses to 412where it may determine a possibility of grey air recirculation andproceed to 414 to not open the ACV, and maintain the ACV at a closedposition. Barometric pressure (BP), if desired, may be measured bycombination temperature/pressure sensor such as sensor 121 of FIG. 1B.

Grey air may be present in the intake manifold in the form of purgedfuel vapors from a fuel vapor canister (such as from purge conduit 76 inFIGS. 1A and 1B), mixture of air and fuel vapors received from apositive crankcase ventilation (PCV) system (such as via PCV conduit 78in FIGS. 1A and 1B), exhaust backwash from an overlap between exhaustvalves and intake valves, and/or exhaust gases received from an exhaustgas recirculation (EGR) system such as those shown in FIGS. 1A and 1B.This mixture of air, exhaust gases, and fuel vapors may includeconstituents that accumulate as semi-polymerized deposits when presentin cooler locations of the engine intake. For example, semi-polymerizeddeposits may build up in an air cleaner in the intake passage since theair cleaner may be cooler. When manifold pressure is higher than TIP ina boosted engine and the ACV is open (or the opening of the ACV isincreased), the mixture of air, fuel vapors, and exhaust gases withinthe intake manifold may flow through the aspirator in the compressorbypass passage (such as conduit 28 of FIG. 1B) towards the air cleaner(such as air cleaner 133 in FIGS. 1A and 1B) in the intake passage.Accordingly, in order to reduce formation of residues from grey airrecirculation via the compressor bypass passage, the ACV may be closedwhen MAP is measured to be higher than TIP.

If, however, it is determined that either boosted conditions are notpresent or that MAP is either equivalent to or lower than TIP, routine400 proceeds to 416.

It will be noted that if the engine is not a forced induction engine(e.g. such as a naturally aspirated engine), routine 400 may skip 410and proceed from 408 directly to 416 (or via 410).

At 416, routine 400 may confirm if a diagnostic trouble code (DTC) hasbeen set. A DTC may be set in the controller upon identification ofdegradation of one or more components within the engine. In someembodiments, a malfunction indicator lamp (MIL) may be activated uponidentification of degradation to alert a vehicle operator. Further,based on the identified degradation, the controller may modify one ormore engine parameters to enable continued reliable engine operation. Assuch, the controller may enable engine operation even though one or morecomponents may be degraded while signaling the vehicle operator toaddress the issue.

Engine operation responsive to diagnosis of engine degradation may betermed as modified engine operation. Modified engine operation mayinclude operating the engine with altered engine parameters such asincreased or decreased EGR flow, modified spark timing, revised fuelinjection, etc. Further, modifications to engine operating parametersmay be based on the identified degradation. As an example, the ACVposition may be dependent on the diagnosed degradation condition. Afirst degradation condition may desire a closed ACV while a seconddegradation condition may require the ACV to be held open. In anotherexample, if an exhaust sensor is determined to be degraded, fuelinjection timing and/or amount may be modified.

Thus, if at 416, routine 400 confirms that a degradation condition hasbeen detected, routine 1000 of FIG. 10 may be activated at 418 todetermine a suitable position of the ACV. The position of the ACV may bebased, as mentioned above, on the type of degradation as well asresulting modified engine operation. Next, at 420, based on routine1000, it may be determined if the modified engine operation in responseto the detected degradation condition allows opening of the ACV. If not,routine 400 proceeds to 422 where the ACV may be closed or retained at aclosed position (e.g. ACV may not be opened). Alternatively, if it isconfirmed at 420 that opening the ACV is desirable in the modifiedengine operation, routine 400 continues to 424 to determine that the ACVmay be adjusted to an open position. The open position may include oneof a fully open position or a position between fully open and fullyclosed. Routine 400 may then end.

Thus, a controller may adjust a position of the aspirator shut-off valve(ASOV) based on engine speed. As such, a first initial position of theASOV may be determined by an existing, measured engine speed. Forexample, the first initial position of the ASOV based solely on enginespeed may be the open (or mostly open, partly open) position when theexisting engine speed is higher than a first speed (Sp_1) and lower thana second speed (Sp_2). By maintaining the ASOV in the open position,considerable motive flow may be enabled through the aspirator.Alternatively, the first initial position of the ASOV may be a closedposition when the existing engine speed is either lower than the firstspeed or higher than the second speed. The first, initial position may,however, be altered if MAP is estimated to be higher than TIP in aboosted engine. In the example of the first initial position of the ASOVbeing the open position, the ASOV may be adjusted to the closed position(e.g. fully closed) if MAP is measured to be higher than TIP to reducegrey air recirculation and formation of deposits in the air cleanerand/or other intake passage components. Further, the first, initialposition of the ACV may be modified based on engine degradationconditions and the resulting modified engine operation. As such, theadjusted ACV position in response to the possibility of grey airrecirculation may also be altered if modified engine operation inresponse to engine degradation requires a different ACV position. Thus,the first initial position of the ACV may be overridden by other engineconditions.

Turning now to FIG. 5, it shows routine 500 for determining a positionof the ACV in a hybrid vehicle system. Specifically, the ACV positionmay be adjusted based on engine speed when the engine is activated forpropulsion, and if engine speed is within the desired range as describedin FIG. 6. The ACV may also be opened for vacuum generation when engineshutdown is commanded and the engine speed falls within a lower desiredrange. Further still, the ACV may be opened or closed based on an oxygencontent of a catalyst during engine shutdown.

At 502, it may be determined if the hybrid vehicle is operating in anengine-on condition. Herein, the engine may be fueled and may becombusting to propel the hybrid vehicle. Alternatively, the engine maybe combusting to recharge a battery in the hybrid vehicle. If it isdetermined that the engine is not operational but is shut down and atrest, routine 500 proceeds to 504 to confirm if an engine-on conditionhas been commanded. The engine may be at rest, and may not becombusting, when the hybrid vehicle is primarily propelled by a motor.As an example, the motor may be the chief force propelling the hybridvehicle during city driving or at lower vehicle speeds. Herein, theengine may be activated for combusting and propelling the hybrid vehiclewhen an increase in torque demand is received.

If an engine-on command has not been issued, routine 500 continues to506 to maintain the engine-off condition, and ends. On the other hand,if the engine has been activated for operation, routine 500 proceeds to508 to determine if the engine-on condition is for vehicle propulsion.For example, the engine may be activated to recharge the battery. Inanother example, the engine may have been activated in response toincreased operator torque demand such as when accelerating. If it isdetermined at 508 that the engine has not been activated for vehiclepropulsion, routine 500 progresses to 510 to determine that the engineis operating for battery recharging. Herein, the engine may becontrolled to operate at idle speed (e.g. 900 RPM) while the battery isrecharged. As such, the engine may not be propelling the hybrid vehicle.The air-fuel ratio may be controlled closely at low engine speeds (e.g.at idle) to reduce noise, vibration, and harshness (NVH) issues. As theengine may be operating at a lower speed during battery recharging, theACV may be maintained at (or moved to) the closed position to reduceadverse effects on air-fuel ratio. Therefore, at 512, routine 500 maydetermine that the desired position for the ACV is the closed position.To elaborate, motive flow through the aspirator may complicate air-fuelratio control during idle speeds and accordingly, the ACV may be closedto discontinue motive air flow through the aspirator. Routine 500 maythen end.

If, however, it is determined at 508 that the engine has been activatedfor vehicle propulsion, routine 500 continues to 514 to determine if theexisting engine speed is between a first, lower speed (Sp_1) and asecond, higher speed (Sp_2). As described earlier in reference toroutine 600, the first lower speed may be based on a transmissionlugging limit of the engine. For example, the first, lower speed may be1200 RPM. The second higher speed (Sp_2) may be based on the engineredline speed. An example second higher speed may be 5000 RPM for anexample engine in a hybrid vehicle.

If the engine speed is determined to be between the first, lower speedand the second higher speed, routine 500 proceeds to 530 to determinethat the desired position for the ACV is the open position. Herein, theopen position may indicate a desired adjustment to the ACV resulting inincreased motive flow through the aspirator. Thus, the open position mayindicate increasing the opening of the ACV. If the engine speed ishigher than the second higher speed (Sp_2) or the engine speed is lowerthan the first lower speed (Sp_1), routine 500 continues to 520 todetermine that the desired position for the ACV is the closed position.Herein, motive air flow through the aspirator may not be desired and theopening of the ACV may be decreased as the ACV is adjusted to a closedposition.

Returning to 502, if it is confirmed that the engine is on andoperational, routine 500 proceeds to 516 to confirm if an engineshutdown has been commanded by the controller. For example, the enginemay be operational and propelling the hybrid vehicle in a motor-offcondition when cruising on a highway. Subsequently, when the hybridvehicle exits the highway to drive on surface streets, an engine-off maybe commanded while activating the motor for propelling the vehicle. Inanother example, the engine may be activated and operational forrecharging the batteries. After the batteries are charged to a desiredlevel, an engine shutdown may be commanded.

If at 516 it is confirmed that engine shut-down has been commanded,routine 500 moves to 518 to check if engine speed is between a thirdspeed (Sp_3) and a fourth speed (Sp_4). Specifically, it may beconfirmed if the engine speed is higher than the fourth speed as well aslower than the third speed. Herein, the third speed (Sp_3) may be lowerthan idle speed. For example, if idle speed is 900 RPM, the third speedmay be 700 RPM. In another example, the third speed may be 500 RPM. Thefourth speed (Sp_4) may be a speed occurring just prior to an imminentengine stop. For example, engine speed at engine stop may be 50 RPM.Herein, the fourth speed (Sp_4) may be 100 RPM. In another example, Sp_4may be 200 RPM. In another example, the fourth speed may be based onreducing engine shutdown shake as the engine comes to rest. Duringengine shutdown, once combustion ceases in the cylinders of the engine,pistons may be compressing and expanding air that is trapped in enginecylinders. As such, excess air flow into the cylinders after fueling isterminated may result in trapped air within the cylinders. Thiscompression and expansion of air may produce torsional pulses that maybe transmitted to the vehicle body resulting in exacerbated NVH issuestermed shutdown shake.

Accordingly, once engine shutdown is commanded and the engine isspinning down to rest with intake throttle closed, the ACV may be openedbriefly for generating vacuum based on an engine speed range and basedon engine shutdown shake. By closing the ACV prior to engine stop,excessive air flow to the cylinders may be decreased leading to areduction in engine shut down shake.

If it is determined at 518 that the engine speed is higher than thefourth speed and is also lower than the third speed, routine 500continues to 522 to determine if an oxygen content stored in an emissioncontrol device is at or near a threshold, Threshold_1. For example, theemission control device may be a three-way catalyst capable of storingoxygen. In particular, oxygen may be stored in the three-way catalystduring lean engine conditions. Lean engine conditions may occur duringengine shut down when the engine is spinning without being fueled andwhen the ACV is opened for vacuum generation (when engine speed isbetween Sp_3 and Sp_4). Air flowing through the aspirator into theintake manifold, the cylinders, and eventually the emission controldevice may result in oxygen being stored in the three-way catalyst.Further, the three-way catalyst may get saturated with oxygen reducingits ability to treat emissions upon an engine restart.

Accordingly, if it is determined at 522 that a level of oxygen stored inthe emission control device is at or near a threshold, Threshold_1(e.g., threshold may be lower than saturation), routine 500 proceeds to520 to determine that the desired position of the ACV is the closedposition. Further, the ASOV may be closed synchronously with an intakethrottle of the engine in the hybrid vehicle. Specifically, as theintake throttle is closed to reduce air flow through the intake passagefollowing the engine shutdown command, the ACV may be closedconcurrently.

On the other hand, if it is determined that the oxygen content in theemission control device is not at or near the threshold (e.g.,considerably lower than the threshold), routine 500 continues to 530 todetermine that the ACV may be opened. Thus, the ACV may be controlledindependent of engine speed. To elaborate, the ACV may not be regulatedbased primarily on engine speed but may also be based on the oxygenstorage content of the emission control device.

It will be appreciated that if the ACV is opened following engineshutdown (between third speed and fourth engine speed), oxygen contentin the catalyst may increase in the duration of air flow through theaspirator. In response to this increase in stored oxygen content, thesubsequent engine restart may include fueling the cylinders initiallywith a richer than stoichiometric air-fuel ratio.

Thus, vacuum may be generated in an engine in a hybrid vehicle via anaspirator during engine-on conditions when the engine is propelling thevehicle and the engine speed is higher than a first lower speed (e.g.,idle speed or transmission lugging limit) and lower than a second higherspeed (such as redline speed). Further, vacuum may also be generated atthe aspirator when the engine is spinning down to rest and engine speedis lower than a third speed (e.g. lower than idle speed) and higher thana fourth speed (speed occurring just prior to an engine stop). However,the ACV may not be opened upon engine shutdown even though the enginespeed is between the third speed and the fourth speed if a level ofoxygen stored in the three-way catalyst is at or near a threshold level.Herein, the ACV position may follow that of the intake throttle.Specifically, the ACV may be adjusted to the fully closed position asthe intake throttle is moved to its fully closed position upon engineshutdown.

It will be noted that a first engine speed may also be termed a firstspeed, a second engine speed may also be termed a second speed, a thirdengine speed may also be termed a third speed, and a fourth engine speedmay also be termed a fourth speed.

Thus, an example hybrid vehicle system may include an engine, an intakemanifold, an intake throttle coupled in an intake passage, a generatorcoupled to a battery, vehicle wheels propelled using torque from one ormore of the engine and the generator, a boost device including acompressor, the compressor positioned in the intake passage upstream ofthe intake throttle, an ejector coupled in a compressor bypass passage,an ejector control valve (ECV), positioned upstream of the ejector inthe compressor bypass passage, regulating motive flow through each ofthe ejector and the compressor bypass passage, a motive inlet of theejector coupled to the intake passage downstream of the compressor, amotive outlet of the ejector coupled to the intake passage upstream ofthe compressor, and a controller with instructions in non-transitorymemory and executable by a processor for, during a first condition,opening the ECV between a first engine speed and a second engine speed,the first engine speed being lower than the second engine speed, andduring a second condition, opening the ECV between a third engine speedand a fourth engine speed, the fourth engine speed being nominallyhigher than that at engine rest, and during a third condition, closingthe ECV independent of engine speed. Herein, the first condition mayinclude an engine-on condition for propelling the hybrid vehicle system,the second condition may include an engine spinning down to rest, andthe third condition may include an oxygen content of a catalyst at anoxygen content threshold. The controller may include furtherinstructions for closing the ECV responsive to one of engine speed beinglower than the first engine speed, engine speed being higher than thesecond engine speed, engine speed being higher than the third enginespeed, and engine speed being lower than the fourth engine speed. Thefirst engine speed may be based on a transmission lugging limit, thesecond engine speed may be based on a redline speed, and the thirdengine speed may be lower than an idle speed. The controller may includefurther instructions for closing the ECV in response to a pressure inthe intake manifold being higher than a pressure at an inlet of theintake throttle.

Turning now to FIG. 7, it depicts routine 700 for determining if engineconditions have changed that may result in altering the position of theACV. Specifically, routine 700 determines if there is a change in engineconditions (e.g., engine speed, manifold pressure, temperature of theACV) that may result in closing the ACV.

At 702, routine 700 may confirm if the engine speed has changed. Asdescribed earlier in reference to routine 600 of FIG. 6, the ACV may beopened when engine speed is determined to be higher than the first,lower speed (Sp_1) and lower than the second higher speed (Sp_2).Therefore, it may be specifically determined at 702, if engine speed hasreduced below the first, lower speed, Sp_1 or if engine speed hasincreased above the second, higher speed, Sp_2. If yes, routine 700continues to 703 to determine that current engine speed is either lowerthan Sp_1 or higher than Sp_2.

An optional confirmation may be performed at 704 to determine if enginespeed is lower than the first, lower speed and vehicle speed (Vs) issubstantially zero. For example, the vehicle may be at rest (and Vs maybe substantially zero) and idling. In another example, engine speed maybe at idle even though the vehicle is moving. The optional confirmationat 704 may be done to ensure that sufficient vacuum is generated whilethe vehicle is moving. If the vehicle speed is higher than zero (e.g.vehicle is moving) and engine speed is lower than the first, lower speed(Sp_1), routine 700 may proceed to 705 to retain the ACV at its openposition. However, if the vehicle speed is substantially zero and theengine speed is lower than the first, lower speed, routine 700 maycontinue to 716. In some embodiments, the controller may skip theoptional confirmation at 704 and proceed directly to 716 from 703.Further, at 716, routine 700 may determine that a change in ACV positionis desired. Specifically, the ACV may be adjusted to a closed position(from an open position) in response to the change in engine speed.

If it is determined at 702 that there is no change in engine speed,routine 700 proceeds to optional check at 706 for a boosted engine. Ifthe engine is naturally aspirated, routine 700 may proceed directly to710 from 702. Specifically, routine 700 may confirm if a change in MAPhas occurred in the boosted engine at 706. As explained earlier inreference to 410 and 412 in routine 400, the ACV may be opened when MAPis lower than or equivalent to the TIP. If a change in MAP is confirmedat 706, routine 700 may then progress to 708 to determine that MAP ishigher than TIP. For example, MAP may be higher than TIP when an engineis exiting boosted conditions and TIP is substantially equivalent to BP.When MAP is higher than TIP, grey air recirculation may occur.Accordingly, the ACV may be adjusted to the closed position at 716 toreduce grey air recirculation.

On the other hand, if no change in MAP is determined in a boostedengine, routine 700 continues to 710 where a temperature of the ACV maybe estimated. The temperature of the ACV may be estimated based on aflow of current to the ACV. As explained earlier, the ACV may be anelectromechanical solenoid valve which may be opened from a defaultclosed position by the passage of current. The flow of current may heatthe ACV resulting in component degradation. Accordingly, the temperatureof the ACV may be monitored so that an increase in ACV temperature abovea threshold temperature may result in a cessation of current flow to theACV allowing a resting period for cooling the ACV. The estimation of ACVtemperature will be described further in reference to FIG. 8 below.

Next, at 712, routine 700 determines if the temperature of the ACV is ator higher than a temperature threshold, Thresh_T. In one example, thetemperature threshold, Thresh_T, may be 200° C. In another example, thetemperature threshold, Thresh_T, may be 150° C. If it is determined thatthe temperature of the ACV is at or higher than the temperaturethreshold, routine 700 continues to 712 to close the ACV. Thus, currentflow to the ACV may be terminated allowing the ACV to fully close.Conversely, if the temperature of the ACV is lower than the temperaturethreshold, Thresh_T, routine 700 progresses to 714 to maintain the ACVat its open position, and then ends.

Thus, a controller in an example engine system may comprise instructionsin non-transitory memory and executable by a processor for adjusting anopening of the aspirator control valve (ACV) based on engine speed, andoverriding the adjusting responsive to a change in engine conditions.The adjusting the opening of the ACV may include increasing the openingof the ACV in response to engine speed being higher than a first speedand lower than a second speed. Further, the change in engine conditionsmay include a change in engine speed, and wherein the overriding mayinclude closing the ACV in response to the change in engine speed. Thechange in engine speed may include one of the engine speed decreasingbelow the first speed and engine speed increasing above the secondspeed. Another example of the change in engine conditions may include achange in intake manifold pressure, and wherein the overriding mayinclude closing the ACV responsive to intake manifold pressure beinghigher than a throttle inlet pressure. Yet another example of the changein engine conditions may include a change in a temperature of the ACV,such as an increase in the temperature of the ACV. Herein, theoverriding may include closing the ACV responsive to the temperature ofthe ACV exceeding a temperature threshold (e.g. Thresh_T of FIG. 7). Thecontroller may include further instructions for closing the ACV inresponse to the engine speed decreasing below the first speed when thevehicle is at rest (e.g. when Vs=0). In other words, the controller mayinclude instructions for not closing the ACV in response to the enginespeed decreasing below the first lower speed (e.g. Sp_1) if the vehicleis moving.

Routine 800 of FIG. 8 illustrates a method for estimating thetemperature of the ACV. Specifically, the temperature of the ACV isestimated based on an amount of current flow and a duration of currentflow.

At 802, routine 800 may confirm that the ACV is commanded open. If not,routine 800 continues to 804 and the temperature of the ACV is notestimated. If yes, routine 800 progresses to 806 to estimate a desiredvoltage for a desired current flow to the ACV. The desired voltage anddesired current flow to the ACV may be estimated by routine 900 of FIG.9. Specifically, the desired voltage and the desired current flow may bebased upon an estimated underhood soak temperature.

Referring to FIG. 9, routine 900 demonstrates an estimation of thedesired voltage and current flow to activate the ACV (e.g. opening theACV). At 902, an underhood soak temperature may be estimated. Underhoodsoak temperature may be a temperature of the air surrounding the engineunder a hood of the vehicle. Underhood temperature (near the engine) maybe inferred based on measurements of various sensors. At 904, routine900 includes using an intake air temperature and an engine coolanttemperature to estimate the underhood soak temperature. A measurement ofintake air temperature may be obtained from a combinationtemperature/pressure sensor, such as sensor 121 of FIGS. 1A and 1B,while a measurement of engine coolant temperature may be received froman engine coolant temperature sensor, such as sensor 112 of FIGS. 1A and1B. In one example, the intake air temperature measurement may besufficient to estimate the underhood soak temperature. In anotherexample, the measurements of the intake air temperature and the enginecoolant temperature may be averaged with a weight function to determinethe underhood soak temperature.

Next, at 906, an electrical resistance and a force constant may beestimated. As such, the underhood soak temperature estimated at 902 maybe used as a reference temperature for estimating the electricalresistance and the force constant due to a magnet coil interaction inthe solenoid of ACV. At 908, the desired current may be determined basedon the force constant along with the desired voltage that may be learnedfrom the estimated electrical resistance. The force constant estimatedfor the solenoid in the ACV may enable learning a minimum current flowneeded to hold the valve open against a spring in the solenoid valve.Further, the electrical resistance along with the desired current enablea calculation of the desired voltage based on Ohm's law.

The ACV, in one example, may be implemented as a spring holding thevalve in a first position with a solenoid opposing the spring force.Solenoids may produce a force that is directly proportional to anapplied electrical current. Further, duty-cycled voltage output driversmay be used for cost reasons rather than current controlled outputdrivers. By forming an estimate of an electrical resistance of thesolenoid, a duty-cycled voltage output may be employed to controlapplied current (since resistance is reasonably known). It is also wellknown in the art that resistance varies with temperature. Thus, byinferring temperature of the ACV, the solenoid resistance may becalculated and a desired duty-cycled voltage may be applied to open ormaintain open the ACV. As such, by applying a smaller yet sufficientelectrical energy, electrical power may be conserved and heating of theACV may be diminished.

It will therefore be appreciated that if the ACV is actuated open usinga calculation as the one in FIG. 9, the ACV may be actuated in a moreefficient manner with a lower power consumption. Further, thetemperature of the ACV may not rise significantly enabling a reductionin resting periods when the ACV is deactivated (and closed) for coolingthe ACV such that the temperature of the ACV decreases to a moresuitable operating temperature.

Returning now to 806 of routine 800 in FIG. 8, upon learning the desiredvoltage and the desired current, routine 800 moves to 808 to estimatethe temperature of the ACV. As such, the estimation method is based onthe current flow, an amount of heat absorbed by the ACV, and an amountof heat dissipated to the surrounding environment. The followingequation may be utilized to estimate the temperature of the ACV:

${Q(k)} = {\left( {{I^{2}*R} - \frac{Q\left( {k - 1} \right)}{T_{h}}} \right)*d\; t}$

-   -   where,        Q may represent heat, I may represent current, R may represent        electrical resistance, t may represent time, and T_(h) may        represent a lump time constant of heat transfer.

In this way, the electrical impedance of the ACV and its thermalconductivity to the surrounding environment may be used to determine atemperature of the ACV.

Thus, an example method for a boosted engine may comprise increasing anopening of an aspirator shut-off valve (ASOV) to allow motive flowthrough an aspirator in response to engine speed between a first, lowerspeed and a second, higher speed. Herein, the first, lower speed may bebased on a transmission lugging limit and the second, higher speed maybe based on redline speed. The method may further comprise closing theASOV when engine speed is lesser than the first lower speed, and whenengine speed is greater than the second, higher speed. The ASOV may beopened via flow of current to the ASOV, and wherein the ASOV may beclosed upon discontinuing the flow of current. The method may includedetermining a voltage and the flow of current to open the ASOV based onan estimated underhood soak temperature, the underhood soak temperatureestimated via inputs from one or more sensors. The method may furthercomprise closing the ASOV in response to a temperature of the ASOVexceeding a temperature threshold. The temperature of the ASOV may bebased on an amount of heat generated by the flow of current to the ASOVand an amount of heat dissipated from the ASOV. The method may furthercomprise during boosted conditions, closing the ASOV in response tointake manifold pressure being higher than a throttle inlet pressure. Itwill be appreciated that the above example method may be for a boostedengine in a hybrid vehicle system.

Turning now to FIG. 10 (including FIGS. 10A and 10B), it illustratesexample routine 1000 for regulating an aspirator control valve (ACV)based on diagnosing an engine degradation condition, and also based on amodified engine operation responsive to the diagnosed engine degradationcondition. Specifically, a position of the ACV may be based on thealtered engine parameters in the modified engine operation.

As described earlier in reference to routine 300 of FIG. 3, detection ofan engine and/or engine component degradation may result in a diagnostictrouble code (DTC) being set by the controller. Further, based on theengine and/or component degradation that has been detected, thecontroller may operate the engine in a management mode that is suitablefor maintaining reliable engine operation even after detection of enginedegradation. As such, the engine may be operated with modified operatingparameters in the management mode. Further, the ACV may be regulated ina different manner in the management mode relative to ACV regulationwhen the engine operation is more robust without any identifieddegradation conditions.

At 1002, routine 1000 may determine if a DTC has been set. If not,routine 1000 proceeds to 1004 wherein the ACV position may be selectedbased on engine speed, temperature of the ACV, etc. as described earlierin reference to FIGS. 4, 5, 6, and 7.

However, if a DTC has been set by the controller, routine 1000 continuesto 1006 to determine the type of engine degradation. Next, at 1008,routine 1000 may confirm if a first type of engine degradation has beenidentified. As an example, the first type of engine degradation mayinclude degradation conditions that do not significantly affect engineoperation. If yes, routine 1000 progresses to 1009 to activate a firstmanagement mode (or management mode 1). Management mode 1 may be a setof engine operating parameters for operating the engine responsive todetection of the first type of engine degradation (also termed, firstengine degradation). Further, the first type of engine degradation mayinclude an adjustment of engine operating parameters that may result inan increase in intake manifold vacuum.

At 1010, it may be confirmed if the first engine degradation includesindication of degradation of the MAF sensor. If yes, routine 1000proceeds to 1012 to actively control air flow via the intake throttle.Further, air flow may be decreased to reduce torque in the engine. As anexample, air flow may be decreased by commanding a reduced opening ofthe intake throttle. For example, the opening of the intake throttle maybe commanded to a reduced percentage opening of 40% (e.g. less thanhalfway open). Further, the opening of the intake throttle may not beallowed to increase to higher than 40%. In another example, the openingof the intake throttle may be commanded to be 30%. It will beappreciated that the degree of opening of the intake throttle may be100% when fully open. Further, the degree of opening of the intakethrottle when fully closed may be 0%. Thus, a 30% opening of the intakethrottle may be a reduced opening relative to the 100% opening when theintake throttle is fully open.

Since a desired EGR flow rate may be based upon readings from the MAFsensor, degradation of the MAF sensor may lead to discontinuing EGR flowat 1014. For example, an EGR valve (such as EGR valve 80) may beadjusted to a closed position to terminate EGR flow into the intakemanifold. Thus, in the above example, modified engine operation inresponse to detection of degradation in the MAF sensor includes reducingair flow through the intake throttle and closing the EGR valve.

Disabling flow of EGR may result in an increase in manifold vacuumlevels since vacuum in the intake is not utilized to draw a portion ofexhaust gas from the exhaust passage. As such, the engine may producesufficient base vacuum. Therefore, at 1024, routine 1000 may confirm ifintake manifold vacuum levels are higher than a first threshold, T_V. Inone example, threshold T_V may be 15 inches of mercury. In anotherexample, first threshold T_V may be 17 inches of mercury. If intakemanifold vacuum is lower than first threshold T_V (level of intakemanifold vacuum is less than T_V), routine 1000 progresses to 1026 wherethe ACV may not be adjusted and may be retained at its position. Forexample, the ACV may be maintained in an open position, if already open.Thus, vacuum may continue to be generated by the aspirator. Further,routine 1000 then returns to 1024.

If, however, it is determined at 1024 that intake manifold vacuum levelis higher (e.g. deeper) than first threshold T_V, routine 1000 continuesto 1034 to close (or maintain closed) the ACV. Routine 1000 may thenend. Herein, sufficient vacuum is available in the intake manifold forsupply to a vacuum reservoir, or a vacuum actuated device when demanded.Further still, additional air flow through the aspirator may not bedesired, since additional torque may be generated due to the excess air.As such, excess torque may not be desired in the management mode orduring modified engine operation.

Returning to 1010, if it is determined that the MAF sensor is notdegraded, routine 1000 proceeds to 1016 to determine if a degradation ofa variable valve timing (VVT) system is detected. If yes, routine 1000continues to 1018 to control intake air flow into the cylinders bycontrolling the intake throttle. The VVT system may be returned to adefault position at 1020 and at 1022, supplementary air flow into theintake manifold may be discontinued. Herein, modified engine operationincludes disabling the VVT system and terminating supplementary air flowinto the intake manifold. For example, the EGR conduit may be closeddisabling EGR flow into the intake manifold, purge flow from the fuelsystem canister may be terminated, and/or air flow from the positivecrankcase ventilation system may be ceased. Thus, the engine operationmay be controlled in a more reliable manner.

By stopping flow of additional air and fuel vapors along with exhaustgases into the intake manifold (e.g., from fuel system canister), vacuumlevels in the intake manifold may increase since base vacuum is not usedto draw these air and fuel mixtures into the intake manifold. Routine1000, therefore, may determine at 1024 if the vacuum levels in theintake manifold are higher (e.g., deeper) than threshold T_V. If intakemanifold vacuum level is lower than threshold T_V, routine 1000progresses to 1026 where the ACV may be retained in an open position, ifalready open. Thus, vacuum may continue to be generated by theaspirator. Further, routine 1000 then returns to 1024. If, however, itis determined at 1024 that intake manifold vacuum level is higher (e.g.,deeper) than threshold T_V, routine 1000 continues to 1034 to close (ormaintain closed) the ACV. Thus, it may be determined that the ACV maynot be opened. Routine 1000 may then end.

Returning to 1016, if degradation of the VVT system is not diagnosed,routine 1000 proceeds to 1028 and determines that another type of firstengine degradation has been detected. As such, routine 1000 depicts twoexamples of the first engine degradation condition such as degradationof the MAF sensor and degradation of the VVT system. If neither of thetwo examples is detected, another component of the engine may bedegraded and may be determined to be a first engine degradationcondition. As such, modified engine operation in response to thedetection of the first engine degradation condition may include a risein manifold vacuum levels. In alternative examples, base vacuum in theintake manifold may not increase in response to the modified engineoperation resulting from identification of the first engine degradationcondition.

Based on the other first engine degradation identified at 1028, anappropriate management mode may be activated with different engineoperating parameters. At 1030, routine 1000 may determine if the ACV isto be closed in response to the modified engine operation. For example,the management mode that is activated in response to the other type ofthe first engine degradation determined at 1028 may demand that the ACVbe closed. If yes, routine 1000 progresses to 1034 to close the ACV orto determine that the ACV may not be opened. If not, routine 1000proceeds to 1032 to maintain the ACV at an open position. Alternately,it may determine that engine conditions do not demand closing the ACV.

It will be appreciated that the examples of MAF sensor degradation andVVT system degradation are included in routine 1000 as examples of thefirst engine degradation condition which may lead to a modified engineoperation that can cause an increase in manifold vacuum levels. Othersimilar degradation conditions may be encountered which could beincluded under the first type of degradation condition without departingfrom the scope of this disclosure.

Thus, an example system for an engine may comprise an engine intakemanifold, an intake throttle coupled in an intake passage, an aspiratorcoupled in a bypass air intake passage across the intake throttle, anaspirator control valve, positioned downstream of the aspirator in thebypass air intake passage, for regulating motive flow through each ofthe aspirator and the bypass air intake passage, a motive inlet of theaspirator coupled to the intake passage upstream of the intake throttle,a motive outlet of the aspirator coupled to the intake passagedownstream of the intake throttle, and a controller with instructions innon-transitory memory and executable by a processor for, responsive toan indication of a first engine degradation condition, closing theaspirator control valve, and discontinuing generation of vacuum via theaspirator. The first engine degradation condition may include anincrease in intake manifold vacuum level above a first threshold level.For example, management of the first engine degradation condition, as inroutine 1000, may comprise an increase in vacuum levels in the intakemanifold as described at 1024. The increase in vacuum levels may occurbecause one or more of EGR flow, canister purge flow, and PCV flow maybe disabled. In one example, the first engine degradation condition mayinclude degradation of a mass air flow (MAF) sensor (as shown in routine1000). In another example, the first engine degradation condition mayinclude degradation of a variable valve timing (VVT) system.

Returning to 1008, if it is determined that the engine degradationdetected is not the first type, routine 1000 continues to 1036 todetermine that a second type of engine degradation has been identified.As an example, the second type of engine degradation may includedegradation conditions that considerably affect engine operation. Next,at 1037 a second management mode (e.g. management mode 2) may beactivated. Management mode 2 may be a set of engine operating parametersfor operating the engine responsive to detection of the second type ofengine degradation (also termed, second engine degradation). In oneexample, the second type of engine degradation may include adjustingengine operating parameters such that they produce a decrease in intakemanifold vacuum levels (or an increase in pressure in the intakemanifold). It will be appreciated that management mode 2 may bedifferent from management mode 1 at 1009.

At 1038, it may be confirmed if the second engine degradation includesan intake throttle that is stuck open. For example, the throttle may bestuck in a fully open or mostly open position and significant air flowmay be entering the engine intake. If yes, routine 1000 continues to1040 to disable and deactivate a plurality of sensors and actuators. Inone example, the EGR valve may be disabled to a closed position.Further, measurements from an EGR sensor may be disregarded. Furtherstill, the EGR sensor may be deactivated. Alternatively, measurementsfrom other sensors may be disregarded by the controller in response tothe detection of the stuck throttle. Further, at 1042, engine operation(e.g., torque produced) may be controlled by regulating fuel injectionand/or by adjusting spark timing. For example, spark timing may beretarded to reduce engine torque. In another example, fuel injectionamount may be reduced to decrease engine torque. Thus, modified engineoperation in response to diagnosing an intake throttle stuck in the openposition may include operating the engine with modified spark timingand/or fuel injection (e.g., injection timing, pulse width, etc.).

Next, at 1052, routine 1000 may determine if manifold vacuum levels havedecreased below a second threshold, T_L. Since the intake throttle isstuck open, pressure in the intake manifold may increase resulting in adecrease in manifold vacuum levels. In one example, second threshold T_Lmay be 5 inches of mercury. In another example, second threshold T_L maybe equivalent to atmospheric pressure. If it is determined that manifoldvacuum levels are higher than the second threshold, T_L, routine 1000continues to 1054 to maintain the ACV in its position. In one example,the ACV may be at a closed position and may therefore be retained in theclosed position at 1054. On the other hand, if it is determined thatintake manifold vacuum levels have decreased below the second threshold,T_L, routine 1000 proceeds to 1062 to determine that the ACV may beopened. As such, the ACV may be adjusted to an open position includingfully open as well as mostly open positions. Therefore, in response tothe increased pressure in the manifold and corresponding reduction inintake manifold vacuum levels, the ACV may be opened for vacuumgeneration. Specifically, an opening of the ACV may be increased inresponse to the intake throttle being stuck open.

Returning to 1038, if it is determined that the intake throttle is notstuck open, routine 1000 moves to 1044 to confirm if the throttleposition sensor (TPS) is degraded. The TPS provides an indication of theposition of the intake throttle to the controller (such as sensor 58 inFIGS. 1A and 1B). If yes, routine 1000 progresses to 1046 to maintainthe intake throttle at a mostly open position. As an example, the intakethrottle may be adjusted to the mostly open position wherein the degreeof opening of the intake throttle is increased. For example, apercentage opening of the intake throttle may be 75%. In anotherexample, the percentage opening of the throttle may be 85%. Further, theposition of the intake throttle may be restrained from furtheradjustment that will reduce the degree of opening of the intakethrottle.

As mentioned earlier, the degree of opening of the intake throttle maybe 100% when fully open. Further, the degree of opening of the intakethrottle when fully closed may be 0%. Thus, a 85% opening of the intakethrottle may be a significantly increased opening relative to the 0%opening when the intake throttle is fully closed.

Since degradation of the TPS sensor render measurements from the TPSsensor unusable, the controller may adjust the intake throttle to themostly open position for sufficient air flow into the engine cylinders.By maintaining the intake throttle in the mostly open (or fully open)position, the engine may continue to produce sufficient torque. As such,engine torque may be controlled via fuel cuts and/or spark timingadjustments. Next, at 1048, various sensors and actuators may bedisabled. For example, the EGR valve may be disabled and adjusted to theclosed position terminating EGR flow once the second engine degradationcondition is identified. Further, measurements from multiple sensors maybe disregarded. For example, measurements from the EGR sensor may bedisregarded. Further, at 1050, torque production may be controlled byadjusting spark timing and/or fuel injection. Thus, the management modein response to detecting a degraded TPS sensor may include adjusting theposition of the intake throttle for higher air flow, and modifying sparktiming, and fuel injection amongst other parameters to control torque.

Next, routine 1000 proceeds to 1052 where it may determine if manifoldvacuum levels have decreased below the second threshold, T_L. Herein,since the intake throttle is held open, pressure in the intake manifoldmay increase (e.g. up to atmospheric pressure) leading to a decrease inmanifold vacuum levels. In one example, second threshold T_L may be 3inches of mercury. In another example, second threshold T_L may be 5inches of mercury. If it is determined that manifold vacuum levels arehigher than (or deeper than) the second threshold, T_L, routine 1000continues to 1054 to maintain the ACV in its position. In one example,the ACV may be at a closed position and may therefore be retained in theclosed position at 1054. In another example, if the ACV is acontinuously variable valve, the ACV may be at a party open position.Herein, the ACV may be retained at its partly open position.

On the other hand, if it is determined at 1052 that intake manifoldvacuum levels have decreased below the second threshold, T_L, routine1000 proceeds to 1062 to determine that the ACV may be opened. As such,the ACV may be adjusted to an open position including fully open as wellas mostly open positions. For example, if the initial position of theACV is the partly open position, at 1062, the ACV may be altered to thefully open position. Therefore, in response to the increased pressure inthe manifold (and resulting lower levels of intake manifold vacuum), theACV may be opened to enable vacuum generation. Specifically, an openingof the ACV may be increased in response to the degradation of thethrottle position sensor.

Returning to 1044, if degradation of the TPS is not diagnosed, routine1000 proceeds to 1056 and determines that another type of second enginedegradation has been detected. As such, routine 1000 depicts twoexamples of the second engine degradation condition such as degradationof the TPS and an intake throttle that is stuck open. If neither ofthese two examples is detected, another component of the engine may bedegraded. For example, the second engine degradation condition mayinclude degradation of one or more sensors providing input to the ACVcontrol algorithm (e.g. routine 300 of FIG. 3). As one example,degradation of the engine speed (or crankshaft speed) sensor may beincluded in the second engine degradation condition. In the embodimentsof FIGS. 1A and 1B, Hall effect sensor 118 (or other type) coupled tocrankshaft 40 may provide measurements of engine speed. Degradation ofHall effect sensor 118 may affect control of the ACV since the positionof ACV may be based on engine speed (e.g. routine 600 of FIG. 6). Asanother example, degradation of a manifold absolute pressure (MAP)sensor (such as sensor 122 of FIGS. 1A and 1B) may also be considered asecond engine degradation condition. Degradation of the engine speedsensor or the MAP sensor may affect adjustments to the position of theACV.

Engine operation may be modified in response to the detection of thesecond engine degradation condition wherein the second enginedegradation condition includes degradation of one or more sensorsproviding input for ACV control. Based on the other second enginedegradation identified at 1056, an appropriate management mode may alsobe activated with different engine operating parameters at 1056. Themodified engine operation may produce a reduction in manifold vacuumlevels. At 1058, routine 1000 may determine if the ACV is to be openedin response to the modified engine operation. For example, themanagement mode that is activated in response to the other type ofsecond engine degradation may demand that the ACV be opened. Toelaborate, since ACV position is largely based on feedback from one ormore sensors (e.g., engine speed sensor, MAP, IAT), degradation of oneor more of these sensors may result in increasing the opening of theACV. To further elaborate, the ACV may not be maintained in a fullyclosed position in response to degradation of one or more sensorsproviding inputs to the ACV control algorithm. In one example, the ACVmay be adjusted to a position midway between fully open and fullyclosed. In another example, the ACV may be adjusted to a mostly openposition.

If it is determined at 1058 that the ACV is to be opened, routine 1000progresses to 1062 to determine that the ACV can be opened. As such, theopening of the ACV may be increased. If not, routine 1000 proceeds to1060 to maintain the ACV at a closed position. Alternately, it maydetermine at 1060 that engine conditions do not demand opening the ACV.

It will be appreciated that the examples of the intake throttle stuckopen and degradation of the TPS are included in routine 1000 as examplesof the second engine degradation condition which may lead to a modifiedengine operation that can cause a decrease in manifold vacuum levels.Other similar degradation conditions may be encountered which may beincluded under the second type of degradation condition withoutdeparting from the scope of this disclosure.

Thus, an example method for an engine may comprise opening an aspiratorshut-off valve in response to diagnosing an engine degradationcondition, the engine degradation condition including a decrease inintake manifold vacuum level below a threshold vacuum level. The examplemethod may further comprise adjusting an engine operating parameterresponsive to diagnosing the engine degradation condition. As describedin routine 1000, one of fuel injection and spark timing may be adjustedin response to the diagnosis of the second engine degradation. Oneexample of the engine degradation condition may include an intakethrottle that is stuck in a mostly open position. Another example of theengine degradation condition may include degradation of an intakethrottle position sensor.

It will be noted that the examples degradations cited above and theassociated modified engine operation may be for a naturally aspiratedengine such as engine 10 of FIG. 1A. While the example routine 1000demonstrates two types of engine degradation (a first type and a secondtype), there may be additional types which may include different changesin engine operating conditions.

Thus, another example method for an engine may comprise closing anaspirator control valve (ACV) responsive to diagnosing a first enginedegradation condition, and opening the ACV in response to diagnosing asecond engine degradation condition, the second engine degradationcondition being distinct from the first engine degradation condition.The first engine degradation condition may include an increase in intakemanifold vacuum level above a first threshold level. An example of thefirst engine degradation condition may be degradation of a mass air flow(MAF) sensor. The method may further comprise discontinuing flow ofexhaust gas recirculation (EGR) responsive to the degradation of the MAFsensor. Another example of the first engine degradation condition mayinclude degradation of a variable valve timing system. Further, thesecond engine degradation condition may include a decrease in intakemanifold vacuum level below a second threshold level. An example of thesecond engine degradation condition may include an intake throttle stuckin a mostly open position. The method may further comprise adjusting oneor more of fuel injection and spark timing in response to the intakethrottle being stuck in the mostly open position. Another example of thesecond engine degradation condition may include degradation of an intakethrottle position sensor. Yet another example of the second enginedegradation condition may include degradation of one or more sensorsproviding input to a control algorithm for the ACV. Example sensorsherein may include an engine speed sensor and/or a MAP sensor. The ACVmay be coupled to a bypass passage across an intake throttle, the bypasspassage including an aspirator. In one example, the ACV may be acontinuously variable valve. In another example, the ACV may be a binaryvalve.

An example ASOV adjustment is now shown with reference to FIG. 11. Inthe example of FIG. 11, the ASOV adjustment is based on engine speed andthe temperature of the ASOV. Map 1100 depicts the state of an ASOV atplot 1102, temperature of the ASOV at plot 1104, and engine speed atplot 1106. Time is plotted on the x-axis and time increases from left toright along the x-axis. The ASOV is shown as a binary valve that can beadjusted to either a fully open position or a fully closed position.ASOV may be an electrically actuated solenoid valve. In otherembodiments, the ASOV may be a continuously variable valve capable ofassuming positions between fully open and fully closed. Further, line1103 represents a temperature threshold (such as Thresh_T of FIG. 7).Furthermore, line 1107 represents a first, lower speed (such as Sp_1 ofFIGS. 5 and 6) and line 1105 represents a second, higher speed, such asSp_2 of FIGS. 5 and 6. As mentioned earlier, the first, lower speed(Sp_1) may be based on a transmission lugging limit, while the second,higher speed (Sp_2) may be based on redline speed for the given engine.As such, the ASOV may be coupled in either a naturally aspirated engineor a forced induction engine within either a hybrid vehicle or anon-hybrid vehicle.

Between t0 and t1, the engine may be idling as shown by plot of enginespeed at idle speed. In one example, the engine may have been coldstarted. The ASOV may be closed during idling conditions (plot 1102),particularly at cold cranking to stabilize air-fuel ratio calculations.Further, since the ASOV is electrically actuated, maintaining the ASOVat the closed position may reduce current draw from the battery whenbattery charge may be lower as at a cold start. As mentioned earlier,the default position of the ASOV may be a closed position whereincurrent may not flow to the ASOV. Accordingly, temperature of the ASOVis lower between t0 and t1.

At t1, engine speed may increase sharply as the vehicle is accelerated.Since engine speed is now above the first, lower speed (line 1107) whileremaining below the second, higher speed (line 1105), the ASOV may beopened at t1. As the ASOV is now actuated to the open position by a flowof current, its temperature may rise gradually as shown by plot 1104. Att2, ASOV temperature may reach the temperature threshold (line 1103). Inresponse to the temperature of the ASOV reaching the temperaturethreshold, the ASOV may be closed at t2 by ceasing current flow to theASOV. The ASOV may be closed at t2 even though the engine speed iswithin the desired range, e.g. between the first, lower speed and thesecond, higher speed. Thus, the position of the ASOV based on enginespeed may be overridden by the temperature of the ASOV increasing abovethe temperature threshold. As such, a resting period may be enabled att2 for the ASOV to cool down. Accordingly, ASOV temperature may reduceafter t2.

At t3, engine speed also decreases below the first, lower speed (line1107), possibly as the vehicle slows down. Further, engine may bespinning at idle speed between t3 and t4. In response to engine speedbeing lower than the first, lower speed threshold, the ASOV ismaintained closed between t3 and t4. At t4, the engine speed risessharply and momentarily reaches the second, higher speed as shown at1111. Therefore, the ASOV may not be opened until engine speedstabilizes between the first, lower speed and the second, higher speed,such as at t5. It will be noted that at t5, the temperature of the ASOVis also lower than the temperature threshold allowing current flow tothe ASOV for opening the ASOV. The ASOV may be maintained open past t5since engine speed remains between the first, lower speed and thesecond, higher speed, and the temperature of the ASOV also remains belowthe temperature threshold.

In this way, an example method of controlling the aspirator controlvalve (ACV) may include adjusting an opening of the ACV based on enginespeed, and overriding the adjusting responsive to a change in engineconditions. For example, the adjusting may include increasing theopening of the ACV in response to engine speed being higher than a firstspeed (Sp_1) and lower than a second speed (Sp_2). In one example, thechange in engine conditions may include a change in engine speed, andwherein the overriding includes closing the ACV in response to thechange in engine speed (such as at t3 of map 1100). The change in enginespeed may include one of the engine speed decreasing below the firstspeed and engine speed increasing above the second speed. In anotherexample, the change in engine conditions may include the temperature ofthe ASOV exceeding a temperature threshold, and wherein the overridingincludes closing the ASOV. Specifically, the ASOV position may beadjusted to a fully closed position (from either a mostly open or fullyopen position) responsive to the temperature of the ACV exceeding thetemperature threshold

Turning now to FIG. 12, an example ACV adjustment based on engine speedand changes in manifold pressure is shown. Map 1200 depicts the state ofan ACV at plot 1202, manifold pressure (MAP) at plot 1204, throttleinlet pressure (TIP) at plot 1206 (short dashes), and engine speed atplot 1208. Time is plotted on the x-axis and time increases from left toright along the x-axis. The example ACV shown is a binary valve that canbe adjusted to either a fully open position or a fully closed position.In other embodiments, the ACV may be a continuously variable valvecapable of assuming positions between fully open and fully closed.Further, line 1205 represents barometric pressure (BP), line 1209represents a first, lower speed (such as Sp_1 of FIGS. 5 and 6) and line1207 represents a second, higher speed, such as Sp_2 of FIGS. 5 and 6.As mentioned earlier, the first, lower speed (Sp_1) may be based on atransmission lugging limit, while the second, higher speed (Sp_2) may bebased on redline speed for the given engine. As such, the example ACVmay be coupled in a forced induction engine within either a hybridvehicle or a non-hybrid vehicle.

Between t0 and t1, the engine may be idling as shown by plot 1208. TheACV may be closed during idling conditions (plot 1202) to maintain adesired air flow to stabilize air-fuel ratio and emissions. Since theengine is idling, the intake throttle may be closed resulting in lowermanifold pressure conditions (plot 1204). Further, TIP may be at orclose to atmospheric (as shown by plot 1206 and line 1205) since theengine may not be boosted when idling. Thus, TIP (plot 1206) is higherthan MAP (plot 1204) between t0 and t1.

At t1, engine speed may rise steeply resulting in an increase in enginetorque that may be utilized for vehicle propulsion. For example, thevehicle may be accelerating to merge with traffic on a highway. As such,the engine may now be boosted resulting in the increase in TIP as wellas MAP. Further, each of TIP and MAP may now be higher than barometricpressure. In the example shown, the intake throttle may be mostly openallowing the MAP to be substantially similar to TIP. Further still, theACV may be opened at t1 as the engine speed is higher than the first,lower speed (line 1209) and lower than the second, higher speed (line1207). Since the intake manifold vacuum level may be lower due toboosted engine operation, opening the ACV may enable vacuum generation.Engine speed remains between the first lower speed and the second higherspeed between t1 and t2, so the ACV may be maintained open in the sameduration. Accordingly, with the ACV held open, motive flow may bedirected through the aspirator from downstream of the compressor (andupstream of the intake throttle). Further, vacuum generated at thethroat of the aspirator may be drawn into the brake accumulator and thevacuum reservoir.

Between t1 and t2, boosted conditions may stabilize and MAP may be aboutthe same as TIP or may be lower than TIP. At t2, boosted conditions maybe reduced as engine speed decreases slightly, but engine speed remainsbetween the first, lower speed (line 1209) and the second, higher speed(line 1207). As the engine exits boosted conditions, TIP may reducefaster and may be substantially equivalent to BP at t2. However, MAP maydecrease at a slower rate than TIP. Consequently, MAP may be higher thanTIP between t2 and t3. Further, a likelihood of grey air recirculationand residue formation at cooler regions of the intake may increase withMAP being higher than TIP (and BP as shown). Accordingly, the ACV isclosed at t2, until MAP reduces below TIP rises at t3. The ACV may beopened at t3 as TIP is higher than MAP. The ACV may be maintained openfor vacuum generation as long as engine speed is between the first,lower speed and the second, higher speed. If the MAP is higher than theTIP, the position of the ACV is overridden and the ACV is adjusted tothe closed position (e.g. fully closed) from an open (e.g. fully open)position.

Map 1300 of FIG. 13 depicts an example ACV adjustment based on enginespeed and detection of engine degradation conditions. As such,identification of engine degradation may result in a modified engineoperation with distinct engine parameters. Modified engine operation maybe termed a management mode. Accordingly, the ACV may be adjusted inresponse to engine conditions based on the modified engine operation.Map 1300 depicts state of the ACV at plot 1302, engine degradationcondition type at plot 1304, manifold vacuum levels at plot 1306, EGRvalve position at plot 1308, intake throttle position at plot 1310, andengine speed at plot 1312. Time is plotted on the x-axis and timeincreases from the left to the right along the x-axis. The example ACVmay be a continuously variable valve capable of assuming positionsbetween fully open and fully closed. Alternatively, the example ACV maybe a binary valve that can be adjusted to either a fully open positionor a fully closed position. Further, line 1305 represents a firstthreshold for intake manifold vacuum level (e.g. first threshold T_V ofFIG. 10), line 1307 represents a second threshold for intake manifoldvacuum level (e.g. second threshold T_L of FIG. 10), line 1313represents a first, lower engine speed (such as Sp_1 of FIGS. 5 and 6)and line 1311 represents a second, higher engine speed, such as Sp_2 ofFIGS. 5 and 6. As mentioned earlier, the first, lower engine speed(Sp_1) may be based on a transmission lugging limit, while the second,higher engine speed (Sp_2) may be based on redline speed for the givenengine. As such, the example ACV may be coupled in a naturally aspiratedengine within either a hybrid vehicle or a non-hybrid vehicle.

Between t0 and t1, the engine speed may be at idle with the intakethrottle at a more closed (e.g. fully closed) position. Accordingly,intake manifold vacuum levels may be considerably higher (or deeper).The EGR valve may be closed during idle conditions. The ACV may also beclosed because the engine is idling (to reduce air-fuel ratio errors)and sufficient intake manifold vacuum is available. Further, between t0and t1, engine degradation has not been detected.

At t1, engine speed increases rapidly in response to torque demand forvehicle propulsion from rest. The intake throttle may be at wide openposition (or more open position, as shown by plot 1310) to providesubstantial air flow. The EGR valve may be closed during wide openthrottle conditions (plot 1308). The ACV, though, may be opened at t2since engine speed is between the first, lower speed and the secondhigher speed. Furthermore, a rapid decrease in manifold vacuum levelsmay be observed during wide open throttle conditions.

Between t1 and t2, the intake throttle may be adjusted to a positionbetween more open and more closed (e.g. halfway between fully open andfully closed), intake manifold vacuum levels may stabilize, and theengine speed may settle between the first lower speed (line 1313) andthe second, higher speed (line 1311). The ACV may be retained at itsopen position to generate vacuum, as intake manifold vacuum levels arelower. Between t1 and t2, as the engine speed stabilizes, the EGR valvemay be opened to enable a reduction in NOx emissions. As the EGR valveis opened gradually, intake manifold vacuum may reduce as the manifoldvacuum is used to draw EGR gases into the intake. As depicted, intakemanifold vacuum may substantially reach the second threshold (line 1307)at t2.

At t2, the controller may detect a first engine degradation condition(plot 1304). In one example, degradation may be detected in a MAFsensor. In another example, degradation in the VVT system may beidentified. Accordingly, the intake throttle may be gradually adjustedtowards the more closed position reducing air flow. It will be notedthat the intake throttle is not fully closed. As mentioned earlier, thedegree of opening of the intake throttle may be 40%. In another example,the degree of opening of the intake throttle may be 30%. The enginespeed may gradually fall while continuing to remain between the first,lower speed and the second, higher speed. In response to the detectionof the first engine degradation, the EGR valve may also be closed (plot1308) at t2 to reduce excessive air flow into the intake. In response tothe adjustment of the intake throttle towards more closed and theclosure of the EGR valve, intake manifold vacuum levels rise graduallysuch that at t3, intake manifold vacuum may be higher than the firstthreshold (line 1305). Since there is sufficient vacuum in the intakemanifold, and excessive air flow may not be desirable, the ACV may beclosed at t3 and may remain closed thereafter.

Between t4 and t5, a duration of time may pass wherein the first enginedegradation condition may be resolved and remedied. For example, thedegraded sensors or degraded systems may be repaired. Thus, at t5, adistinct drive cycle may ensue wherein the engine is robust. Between t5and t6, engine speed is lower than the first, lower speed (line 1313)and the intake throttle is at the more closed position. Accordingly,intake manifold vacuum level is higher (e.g. deeper) and the ACV isclosed since engine speed is lower than the first, lower speed. The EGRvalve is closed and no degradation is detected.

At t6, engine speed rises gradually and stabilizes between the first,lower speed and the second, higher speed as the intake throttle isopened to a position between mostly open and mostly closed. As shown,the opening of the intake throttle may be increased to moderately openfrom the more closed position at t5. Simultaneously, due to theincreased opening of the intake throttle, intake manifold vacuum levelsmay decrease between t6 and t7, and the ACV may be opened for vacuumgeneration. As depicted in the example, the ACV may be opened partlysuch that the ACV may be at a position between fully open and fullyclosed. This may be possible with a continuously variable ACV.Alternatively, the ACV may be adjusted to the fully open position, if abinary valve, as shown by dashed line 1303. As such, opening the ACVbetween the first, lower speed and the second, higher speed ensures thatthe excess air flow does not adversely affect air-fuel ratio control.The EGR valve may be gradually opened past t6.

At t7, the controller may detect and signal a second, engine degradationcondition (plot 1304). In the depicted example, the second enginedegradation condition may include the intake throttle being stuck open(plot 1310). In another example, the second engine degradation conditionmay include detection of a degraded throttle position sensor, such assensor 58 in FIGS. 1A and 1B.

In response to the signaling of the second engine degradation conditionat t7, a modified engine operation may be initiated wherein engineparameters may be adjusted to provide reliable engine operation. Forexample, since the intake throttle is stuck in a mostly open positionallowing a larger proportion of air to flow into the engine, torqueproduction may be controlled by adjusting spark timing and/or fuelinjection (e.g. injection timing, pulse width, etc.). Further, inresponse to the signaling of the second engine degradation condition,the EGR valve may be closed at t7. With the modified engine operationand adjusted spark timing and/or fuel injection, engine speed may reduceafter t7. However, engine speed may remain higher than the first, lowerspeed. Further, with the intake throttle being mostly open, intakemanifold vacuum levels may decrease below the second threshold (line1307). In response to intake manifold vacuum levels reducing below thesecond threshold at t7, the ACV may be opened (or maintained open) forvacuum generation. As shown in map 1300, the ACV may be opened to thefully open position at t7. This may occur in an ACV that is continuouslyvariable.

In this way, an example method for an engine may comprise determining afirst position of an aspirator shut-off valve (ASOV) responsive toengine speed, and adjusting the first position of the ASOV based ondetection of an engine degradation condition. The first position of theASOV may include a mostly open position responsive to engine speed beinghigher than a first speed (line 1313 of map 1300) and lower than asecond speed (line 1311 of map 1300), and wherein adjusting the firstposition includes adjusting the ASOV to a mostly closed position when afirst engine degradation condition is detected (e.g., at t3 in map1300). The first engine degradation condition may include an increase inintake manifold vacuum above a first threshold level (e.g., plot 1306 att3 in map 1300). In another example, the first position of the ASOV mayinclude a partly open position as at t6 in map 1300 (plot 1302), andwherein the adjusting includes adjusting the ASOV to a fully openposition when a second engine degradation condition is detected (as att7 in map 1300). An example of the second engine degradation conditionmay include a decrease in intake manifold vacuum below a secondthreshold level such as due to a throttle stuck in the mostly openposition.

FIG. 14 presents map 1400 illustrating an example aspirator controlvalve (ACV) adjustment in response to engine speed and oxygen content inan emission control device. The ACV in the depicted example may becoupled in an engine (e.g., naturally aspirated engine, forced inductionengine) included in a hybrid electric vehicle (HEV). The hybrid electricvehicle may be a series hybrid, a parallel hybrid, or a series-parallelhybrid vehicle. Map 1400 presents changes in an oxygen content of acatalyst at plot 1402, air-fuel ratio (AFR) at plot 1404, engineoperation at plot 1406, motor/generator operation at plot 1408, changesin a battery state of charge (SOC) at plot 1410, state of the ACV atplot 1412, and engine speed at plot 1414.

Time is plotted on the x-axis, and time increases from the left of thex-axis to the right of the x-axis. The example ACV shown is a binaryvalve that can be adjusted to either a fully open position or a fullyclosed position. In other embodiments, the ACV may be a continuouslyvariable valve capable of assuming positions between fully open andfully closed. Map 1400 further includes line 1401 representing athreshold oxygen content in the catalyst (such as Threshold_1 of FIG.5), line 1403 representing stoichiometric AFR, line 1405 representing afirst higher SOC threshold for battery SOC and line 1407 representing asecond lower SOC threshold for battery SOC, line 1411 representing asecond, higher engine speed (Sp_2), line 1413 representing a first,lower engine speed (Sp_1), line 1415 indicating idle speed (e.g. 900RPM), line 1417 representing a third engine speed (Sp_3), and line 1419indicating a fourth engine speed (Sp_4). As described earlier inreference to FIG. 5, the third engine speed may be a speed lower thanidle speed for the given engine. The fourth engine speed may be anengine speed that is nominally higher than that at an engine shut down.As an example, engine speed at engine shut down may be 50 RPM. Herein,an example fourth engine speed may be 100 RPM.

Between t0 and t1, the hybrid vehicle system may be operating in anengine-off mode (plot 1406) with the hybrid vehicle being propelledusing motor torque (plot 1408). Since the engine is shut down and atrest, there is no change in the oxygen content of the catalyst (plot1402), the ACV is maintained closed, and the AFR is not plotted.Further, since the motor is powering vehicle motion, battery SOC maygradually reduce between t0 and t1.

At t1, the engine may be commanded “ON”. For example, the engine may beactivated when an operator torque demand increases. The motor may beturned “OFF” at t1 (if motor torque is not required), as shown. Inanother example, the motor may continue to be operated (e.g., at areduced speed) to provide a reduced motor torque demand. As the motor isdeactivated, the battery SOC does not change between t1 and t3 whereuponthe motor may be re-activated. Further, at t1, the engine may beoperated with a richer than stoichiometric AFR (AFR_1 of plot 1404) forimproved combustion and catalyst performance. In response to the enginecombusting at richer than stoichiometric AFR, the oxygen content of thecatalyst reduces. Further still, the engine speed may transition fromrest through idle speed into the range between the first, lower speed(Sp_1) represented by line 1413 and the second, higher speed (Sp_2)indicated by line 1411. As shown, engine speed attains a speed betweenline 1411 and line 1413 at t2 whereupon the ACV is opened from itsprevious closed position. The ACV may be maintained open in the durationthat engine speed remains between the desired range (e.g. between Sp_1and Sp_2). As explained earlier in reference to map 1100, an increase inthe temperature of the ACV may result in closing the ACV irrespective ofengine speed (e.g., not based on engine speed), though this scenario isnot shown in the example operation of map 1400.

At t3, an engine shut down may be commanded and the engine may bedeactivated while simultaneously activating the motor. Accordingly,battery SOC may reduce past t3. As the engine slows down and enginespeed falls below the first, lower speed (Sp_1) at t4, the ACV may beclosed. The ACV may remain closed as engine speed transitions from thefirst, lower speed past idle speed. It will be noted that oxygen contentin the catalyst is sufficiently below the oxygen content threshold (line1401) when the engine is switched off at t3. As engine speed reaches thethird speed (Sp_3 indicated by line 1417) at t5 and decreases, the ACVmay be actuated open at t5 for additional vacuum generation. As such,the intake throttle may be closed once engine shut down is commanded. Byallowing a smaller air flow through the aspirator, vacuum may begenerated before the engine reaches rest while nominally pumping airinto the catalyst. Since the oxygen content in the catalyst is lowerthan the oxygen content threshold, the catalyst may be able to storeadditional oxygen from the excess air flow through the aspirator.Therefore, the ACV may be opened at t5. In response to the engine speedfalling below the fourth speed at t6, the ACV may be closed. It will beobserved that oxygen content in the catalyst increases due to the excessair flowing into the catalyst when the ACV is open between t5 and t6. Aswill be noted, the fourth speed is just higher than an engine at rest.

The engine may be at rest between t6 and t7 while the vehicle is beingpropelled primarily by the motor. Battery SOC decreases gradually fromt3 as the motor is entirely responsible for vehicle motion, and at t7battery SOC reaches the second lower SOC threshold (line 1407) whereuponthe engine may be activated for battery regeneration. At t7, the engineis commanded “ON” and engine speed rises from rest to idle and remainsat idle (e.g. 900 RPM) as the battery is charged. Since engine speeddoes not reach the desired range, between the first, lower speed (line1413) and the second, higher speed (line 1411), the ACV is maintainedclosed between t7 and t9. Herein, the engine may not propel the vehiclebut may be primarily used for battery regeneration. Accordingly, batterySOC rises between t7 and t8.

It will also be noted that the initial AFR (AFR_2) when the engine iscommanded “ON” at t7 is richer than the initial AFR (AFR_1) when theengine is commanded “ON” at t1. The AFR at t7 may be richer than that att1 since there may be excess oxygen stored in the catalyst during theengine shutdown phase between t5 and t6. As depicted in map 1400, oxygencontent at t1 is lower than oxygen content at t7. As will be observed,oxygen content at t6 is higher than the oxygen content stored at t5 dueto excess air flow received at the catalyst from the aspirator. Forexample, the stored oxygen content at t0 (and the resulting AFR at t1)may be lower than the stored oxygen content at t6 (and the resulting AFRat t7) since the ACV may not be opened for vacuum generation followingthe previous engine shutdown.

At t8, the battery SOC is close to the first higher SOC threshold (line1405), but not at the first higher SOC threshold allowing a margin forbattery recharging during braking events in the electric mode(engine-off mode). In response to the battery SOC being close to thefirst higher SOC threshold, a shutdown command may be communicated tothe engine at t8. The engine may then spin unfueled to rest. As enginespeed falls from idle speed to the third speed at t9, the ACV may beactuated open. It will be noted that oxygen content in the catalyst issubstantially below the threshold oxygen content at t9. Accordingly, theACV is opened for vacuum generation at t9. Thus, the position the ACVmay be adjusted based on engine speed being between the third speed andthe fourth speed, as well as the oxygen storage capacity of thecatalyst. The ACV remains open for a brief period between t9 and t10 andin response to the air flowing into the catalyst, oxygen content in thecatalyst increases between t9 and t10. At t10, engine speed reducesbelow the fourth speed and may reach rest by t11. In response to enginespeed reaching the fourth speed at 10, the ACV is also closed at t10.

Between t11 and t12, a duration of HEV operation may elapse including anengine-on duration. As such, the duration of HEV operation with theengine-on condition is not shown in FIG. 14. At t12, the engine may beoperating and propelling the vehicle while the motor is “OFF”. Further,since engine speed is between the first, lower speed (line 1413) and thesecond, higher speed (line 1411) at t12, the ACV is open. Further still,the AFR may be nominally leaner than stoichiometric resulting in agradual increase in the oxygen content of the catalyst between t12 andt13.

At t13, an engine shut down command may be issued and the engine may beturned “OFF” as the motor is activated for vehicle propulsion. The ACVmay be maintained open until t14 when engine speed reduces below thefirst, lower speed (line 1413). Oxygen content in the catalyst continuesto increase until t14 due to air flow received via the aspirator as theACV is open. At t14, the ACV may be closed since the engine speed islower than the first, lower speed. As engine speed falls past idlespeed, and reduces below the third speed (line 1417) at t15, the ACV mayremain closed since oxygen content in the catalyst is substantially atthe oxygen content threshold (line 1401). Thus, the ACV position may beadjusted responsive to the oxygen content of the catalyst. As such, theACV may not be opened following a shutdown command to the engine whenengine speed is between the third speed and the fourth speed if theoxygen content of the catalyst is substantially at the oxygen contentthreshold.

An intake throttle of the engine (not shown in FIG. 14) may be adjustedto a fully closed position in response to the engine shutdown command att13. It will be noted that the ACV is depicted as closing at t14 eventhough the engine shutdown command is issued at t13. However, the timeperiod between t13 when engine shutdown is commanded and t14 when enginespeed reduces below the first, lower engine speed (line 1413) may bebrief. Thus, the ACV may be adjusted to its fully closed position (fromopen) at substantially the same time as the intake throttle is moved toits fully closed position since the duration between t13 and t14 may beshort.

Thus, an example method for an engine in a hybrid vehicle may comprise,during an engine-on condition for vehicle propulsion, opening anaspirator shut-off valve (ASOV) between a first engine speed (Sp_1) anda second engine speed (Sp_2), the first engine speed being lower thanthe second engine speed, and following a first shutdown command to theengine, opening the ASOV between a third engine speed (Sp_3) and afourth engine speed (Sp_4), the fourth engine speed nominally higherthan an engine stop. The method may further comprise, during theengine-on condition for vehicle propulsion, closing the ASOV responsiveto a temperature of the ASOV exceeding a temperature threshold. Themethod may also comprise, following the first shutdown command to theengine, opening the ASOV responsive to an oxygen content of an emissioncatalyst being lower than a threshold. The method may further include,during an engine restart following the first shutdown command, operatingthe engine with a richer than stoichiometric air-fuel ratio. The methodmay additionally comprise, following a second shutdown command to theengine, closing the ACV irrespective of engine speed. Herein, the ACVmay not be opened because the oxygen content in the emission catalyst isat or near the oxygen content threshold. The ASOV may be closedsynchronously with closing of an intake throttle of the engine in thehybrid vehicle.

In this way, an aspirator control valve (ACV) may be regulated based onengine speed. By modulating the ACV based on engine speed, operation ofthe aspirator and the ACV may be reliably tested during vehicleemissions tests. As such, using engine speed as the parameter to decideACV position may enable a more simplified ACV control algorithm.Further, the position of the ACV selected based on the engine speed maybe altered based on a temperature of the ACV, and modified engineoperation responsive to engine degradation diagnoses. By closing the ACVwhen the temperature of the ACV exceeds a temperature threshold, ACVdegradation may be reduced while enhancing its operation. By adjustingthe ACV position based on modified engine operation responsive to enginedegradation conditions, issues such as air flow errors and low vacuummay be addressed. Furthermore, an ACV in a hybrid vehicle may also beregulated based on engine speed following an engine shutdown and anoxygen content in an emission catalyst. Accordingly, catalystperformance may be enhanced while ensuring emissions compliance andproviding sufficient vacuum.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for a hybrid vehicle system, comprising: following ashut-down command to an engine, opening an aspirator control valve (ACV)between a first engine speed and a second engine speed, the first enginespeed being lower than an idle speed and the second engine speedoccurring before an imminent engine stop.
 2. The method of claim 1,further comprising closing the ACV when engine speed decreases to belowthe second engine speed.
 3. The method of claim 2, further comprising,during vehicle propulsion with an engine-on condition, opening the ACVin response to engine speed being higher than a third engine speed andlower than a fourth engine speed.
 4. The method of claim 3, wherein thethird engine speed is based on a transmission lugging limit and thefourth engine speed is based on a redline speed.
 5. The method of claim4, further comprising closing the ACV when engine speed is lesser thanthe third engine speed, and when engine speed is greater than the fourthengine speed.
 6. The method of claim 5, wherein opening the ACV includesflowing current to the ACV, and wherein closing the ACV includesdiscontinuing the flowing of current.
 7. The method of claim 6, whereina voltage and the current to open the ACV are determined based on anestimated underhood soak temperature, the underhood soak temperatureestimated via inputs from one or more sensors.
 8. The method of claim 7,further comprising closing the ACV in response to a temperature of theACV exceeding a temperature threshold.
 9. The method of claim 8, whereinthe temperature of the ACV is based on an amount of heat generated bythe flowing of current to the ACV and an amount of heat dissipated fromthe ACV. 10-15. (canceled)
 16. A method for an engine in a hybridvehicle, comprising: following a first shutdown command to the engine,opening an aspirator shut-off valve (ASOV) between a first engine speedand a second engine speed, the second engine speed being nominallyhigher than that at an engine stop; and following a second shutdowncommand to the engine, closing or maintaining closed the ASOVirrespective of engine speed.
 17. The method of claim 16, wherein,following the first shutdown command to the engine, the ASOV is openedbetween the first engine speed and the second engine speed responsive toan oxygen content of an emission catalyst being substantially lower thanan oxygen content threshold.
 18. The method of claim 17, furthercomprising, during an engine restart following the first shutdowncommand, operating the engine with a richer than stoichiometric air-fuelratio.
 19. The method of claim 18, wherein following the second shutdowncommand to the engine, the ASOV is closed or maintained closedresponsive to the oxygen content of the emission catalyst being at orhigher than the oxygen content threshold.
 20. The method of claim 19,wherein the ASOV is closed synchronously with closing of an intakethrottle of the engine.